Magic Numbers for Max FE?
 

I've been wondering if there is a magic number for getting the most mileage out of your car? Out here the speed limit is 65 on the freeway, if I drive 65 and put the car on cruise control I get something like 46mpg, but if I slow to 63 I bump up my mpg, but piss off the people behind me, at 68 I get varying results, but mostly 50-60 miles per gallon. So, I've determined, very unscientifically mind you, that 68 is a good speed to drive. What I'm trying to figure out is what speeds help to maximize FE while maintaining freeway speed. Since in the city, between 30-40 you can get the electric motor to take over at any time given you have enough battery. The reason I ask is because I see many Priuses driving by at speeds I'd estimate at 70-80 miles per hour. I've driven 70-75 and seen various results, some including 73mpg, so I wonder if they know something I don't. Does this make sense? Here's what you should do if you want to help.

*Your make, model and year (I know it's probably in your profile, but humor me)
*The legal speed limit in your area
*Passenger's Yes/No. Any load whatsoever?
*Your "magic" number

In my case it's:
*2005 Toyota Prius
*65 mph
*no passengers car is basically empty
*68 until I find another

In theory, I would guess that under ideal conditions this would give everyone the same ability to get the most FE out of their car, while maybe even learning something they didn't know about it.

Re: Magic Numbers for Max FE?
 

I travel in the far right lane, and venture to the next left lane if the right one clogs up.

If the divided freeway has only two traveling lanes:
70MPH limit I'll go 65-68 with traffic, if there's nobody behind it will sag to lower 60's.
65MPH limit I'll go 62-65, same traffic rules as above.
55MPH limint is 55-62, same traffic rules.

Mind you I'll go faster in the valleys and low areas than at the top of hills.
If there is less traffic I'll let it sag more ove the hill tops.

I avoid +65MPH unless neccessary.

Re: Magic Numbers for Max FE?
 

Aerodynamic resistance is proportional to the **square** of the velocity. At speeds under 35 or so, other factors come into play, but above 35 it is effectively all about wind resistance. Simply, as Hot_Georgia says, slow down as much as you can on the highway.

I strongly recommend you track down Wayne Brown's Palm program that simulates Prius II mpg under different driving conditions. If you do not own a palm pilot, OS simulators for windows and Macintosh exist. It is a *real* eye opener.

Re: Magic Numbers for Max FE?
 

Wayne, among others, have shown that the ideal speeds on the Toyota Prius II are between 35-40 MPH. The faster you go than that, the worse your mileage. The slower, the worse as well.

Re: Magic Numbers for Max FE?
 

Ideal while you have battery charge, though, right? Once you reach a certain point, you've got no battery and therefore you join the "common" cars with above average gas mileage. What I mean is that I can drive 68 and average 50-60 mpg by the computer's reasoning. That's a good number considering that a lot of people here can't hit it. I have been keeping tabs on my tanks since I discovered this site, and while I don't have my signature posted here, I do have it on another site where at this moment I am sitting at a nice 52.xx mpg. You can see my stats listed under the Silver Millenium Falcon. Nearly my entire drive is freeway and while I'm still learning to drive the car with the utmost FE in mind I'd say my numbers are pretty good.

Re: Magic Numbers for Max FE?
 

I seriously doubt anyone with a Prius is getting 73mpg at speeds over 70mph unless it is down hill or with the wind. Jason is correct in saying that the ideal speed for mileage is much slower, around 40mph. Of course traffic forces a compromize. Personally I tend to drive around 45mph most of the time.

Re: Magic Numbers for Max FE?
 

Red,
I'm not sure what you mean. At optimum speed, the Prius trades between engine on and off. When it's on, it sometimes replenishes the battery. Yet, <40mph is slow enough that the motor can solely propel the automobile.

Re: Magic Numbers for Max FE?
 

It is the wind resistance that makes the speed ideal not the charge in the packs. As has already been said if you go too slow you are not in top gear so you lose mpgs. If you go much faster wind resistance goes up and once again you lose mpgs. Wind resistance goes up with the square of speed so it takes twice as much power to push a car 70 as it does 50.

Re: Magic Numbers for Max FE?
 

So, what you're saying is that when I drove in to work today at ~70 mph (I was running late) and actually increased my MPG for the straight, flat land that you can't drive fast and still maintain good FE? If that's true then one of the following must also be true: a. my car is different from yours b. my computer is malfunctioning c. I'm a liar
I'm just telling you what I see, obviously the car doesn't maintain a steady 70 MPG at 73 MPH, for long stretches, that wasn't my point I've seen it for minutes at a time, it's not just a momentary thing. At 68 the car will on straight, flat land the car will get me over 50 MPG it will dip into the 40's occasionally, but it goes right back up and maintains it for miles at a time. I wish I could prove it to you, but short of video nothing would do so. I do notice though that when I get that mileage that the electric motor is very frequently pitching in, never dipping below the third bar, and also mind you that this is with cruise control on and I never get traffic.

Re: Magic Numbers for Max FE?
 

I don't believe he was saying a, b, or c. I believe he was saying that you would have gotten even better at a lower speed.

If that's not correct, Lakedude, feel free to correct me.

Friendly & contructive - that's our motto.... Not really, but it could be.

Re: Magic Numbers for Max FE?
 

Red, until you pick up WB's simulator, I thought you may be interested in a few numbers ..

No wind, no AC, sea level, summer petrol.

mph .. mpg
61 ... 60.78
64 ... 58.11
68 ... 54.75
71 ... 52.36
76 ... 48.65

My nmeumonic that I remember is that the Prius is part of the 60/60 club :)

Oops, I just saw that I had the Cd at 0.25 rather than 0.26. The mpg's are off by one mpg or so .. Sorry

Re: Magic Numbers for Max FE?
 

What I'm saying though is I've driven 65 and gotten worse mileage. That's why I decided to speed up and I ended up getting better (??) going slower is fine, but I just end up getting everyone mad at me, especially on the two lane highway I drive. I don't mind driving slower and I do so when I can afford the time. My point in starting this thread was to see if there was somehow a speed that would magically help everyone increase mileage, apparently not, though. I'm not getting hostile or anything, it just seems like you're throwing out programs and stuff that simulate this and that when I'm telling you I've actually bettered my mileage with increased speed.

Re: Magic Numbers for Max FE?
 

I would guess that there are other infuences that may have gone unnoticed, e.g., elevation decline or wind shift (or driving direction). There are times when my mileage shoots up (or down) and I don't know why - usually it's elevation changing. And you can't see it. You have to use the NAVI or GPS to tell.

If you get out on, say, a 5 mile stretch of road and try different speeds repeating the same stretch in the same direction, it will probably be the best simulation you can get without running something like the WB simulator program.

Re: Magic Numbers for Max FE?
 

What Tink says :)

Wind in particular has an *enormous* influence, and is probably the culprit in day to day variations that are seen.

E.g., a 5 mph tailwind driving 69 mph will increase your mpg from 64.78 to 70.53 ! I think the change approximates car speed in the opposite direction, but really have not played around with the simulator enough to be sure. So if you drive into a 10 mph wind at 50, your mpg will approximate driving 60 mph without any wind.

New Mexico gets pretty windy, so I have taken to looking at the weather report to try and time my trips. I know -- that is rather extreme -- but it makes quite a difference.

Re: Magic Numbers for Max FE?
 

Correct. You may do great at 70 mph, but you'll do really great at 50 mph.

Re: Magic Numbers for Max FE?
 

Ok - I'm jumping in a little late here, and I know there's been a bunch of viewpoints refuting Red's answer...but I'm going to join him in this debate - to the extent that I notice certain speeds returning greater values on the instantaneous - and that speed is at 8 mph within each 10mph range.

To wit - 38 / 48 / 58 / 68

I'm not going to say that I get better mileage at 68 vs 48 - indeed, 48 is about the sweetest spot for me - I can now peg the instantaneous at 80mph for a couple of minutes or more on level ground, and hold 70 with some ease when I'm around that speed. This is dependent on temperature. So, in this respect, I'll join Lakedude - in my suburban loop, I'll keep between 42 and 48, depending on traffic. And that's my best, per the FCD (I know, it's not called that in the Honda, but it's so much easier than typing 'instantaneous' all day :( The only problem is that I can't sustain a steady speed in suburban driving, and I won't travel 48mph on the interstate. So I'm limited to see if the mileage actually proves true to the FCD, were I to travel long enough at that speed, largely unimpeded.

Where this largely comes into play for me, is that I find it *easier* to hold a steady speed while still dropping back on the throttle for that extra 20%, at those points on the speedo. The lower end of each 10mph range, I tend to lose speed on level ground when I ease up on the throttle to load the engine efficiently, and if I don't correct it, wind up eventually dropping down to the next lower gear (42mph is where 5th gear kicks in on the AH, and TC lockup occurs at 48mph or so). That's why I think 45-48 is the optimum speed (for me at least) - the driveline of the AH is optimized at that speed, and speed in excess of that, produces diminishing returns.

I remember when I drove to Madison w/ Xcel, and I told him that it was easier for me to hold 48 than 42, et al. I don't think he agreed with me, but he didn't argue the point, and I thought that maybe I *was* imagining things. But then I saw this thread. And I'm here to say that I think there's something to this. Can I back up my hypothesis w/ science or engineering? Not yet. But I've got 4 months and 7500 miles of experience behind me at this point ;)

All that said, I find myself these days pretty much maintaing the limit or even a little under, and I find it almost impossible to accellerate from 40 to 50, for example, before my next stop light, etc makes me slow down. The nice thing is that now, I almost never take the car out of VCM while accellerating any more (Xcel noticed how easily VCM could be deactivated when he drove the car).

Re: Magic Numbers for Max FE?
 

Thanks for somewhat backing me up. I understand that slower is better, but in that case why don't I get like a billion miles to the gallon when I'm driving 15 miles per hour?

Re: Magic Numbers for Max FE?
 

Well, your Prius is optimized for 35-40 MPG, so you can start by going 35-40 instead of 15 ;) But, in all seriousness, you can't get a billion miles to the gallon for a couple reasons: current technology is far too inefficient to harvest all of the energy, and there isn't enough energy in gasoline to get you there, even at 100% efficiency.

Re: Magic Numbers for Max FE?
 

Hi Red_The_Impaler:

___You are if your Prius II is in stealth mode which is where it should be. You will pay for it later with the recharge however :(

___The reason 33 - 35 mph on a relatively flat and windless road in a Prius II or Insight 5-speed work so well is that they are at a minimum RPM and power to keep the car from decelerating and maximum gear ratio to keep the RPM’s at their minimum. You would be surprised to see the heat losses of a gear train as RPM’s rise … At 15 mph, you are probably not pushing the highest ratio and the ICE would be lugging severely if it was.

___Good Luck

___Wayne R. Gerdes
___Waynegerdes@earthlink.net

Re: Magic Numbers for Max FE?
 

I can say that I have never been able to achieve 70 MPG unless my speed was below 55 MPH. But that doesn't mean that it can't be done. Two things that could have contributed to your 73 MPG was a tail wind and/or a decrease in elevation.

I have done a lot of testing at different speeds and have developed a speed vs MPG curve for MY car. Under optimal conditions, warm temps, no air conditioning, no significant winds:
- 70MPH = 50MPG
- 65MPH = 55MPG
- 60MPH = 60MPG
- 55MPH = 65MPG
- 50MPH = 70MPG
- 45MPH = 75MPG
- 40MPH = 80MPG
- 35MPH = 85MPG

The most important thing is to only consider round trips. That way you can rule out a change in elevation. I also carry an altimeter on board which reports elevation in increments of 5 ft. Watching the altimeter is an eye opening experience. When I thought I was climbing, I was actually flat or falling, and vice versa. I now rely on the altimeter instead of my instincts.

Re: Magic Numbers for Max FE?
 

Hi Krousdb:

___Thanks for adding the Prius II’s, Speed vs. FE dataset.

___With that, comes a lot of questions … Are you setting up your Prius II like most hypermilers w/ high tire pressures, low kinematic viscosity synthetics at half way between the hi/lo mark, windows tight above 30 mph, etc.? How about acceleration? Fast but smooth enough to get the ICE up and running from launch, slow crawl up to cruising speed via EV with a smooth transition into the ICE, or something in between? Are there any tips/tricks on using Max Fan w/out A/C in a Prius II for summer temp hypermiling? I remember reading how you love cruise but have never read that you have “Driven w/ Load”? I ask this because I remember reading how a Graham Scanner helped Rick Reese nail down a 70 + mpg tank in his Prius I using that technique. I have also read about attempting to keep a Prius II’s HSD from Regen as well as Propulsion when attempting a long coast to a stop. It sounds as if you use the energy flow screen as feedback to guide a very light touch of the accelerator when coasting to keep regen/propulsion at bay? Do you use a similar technique in your Prius or are your travels more conducive to other, less intrusive FE techniques?

___I have so little experience with the HSD/eCVT based automobiles and you just never know when this kind of knowledge could come in handy ;)

___Good Luck and thanks in advance.

___Wayne R. Gerdes
___Waynegerdes@earthlink.net

Re: Magic Numbers for Max FE?
 

Wayne,
Before I answer your questions, let me explain a few things that I have discovered about HSD. As it turns out, there is a magic speed. On my Prius II that speed is 42 MPH. Maximizing FE is all about reducing resistance. The culprits are aero drag, tire rolling resistance, CVT/MG friction and ICE friction. Of course, one can reduce aero drag by driving slower. But one can eliminate ICE friction completely as long as the speed is below 42. This is because the MG’s reach their maximum RPM at approx 42MPH, which forces the ICE to spin to prevent damage to the MG’s. So at speeds above 42, the ICE must spin. This results in added friction which must be compensated for to maintain speed.

Wayne Wrote:
Are you setting up your Prius II like most hypermilers w/ high tire pressures, low kinematic viscosity synthetics at half way between the hi/lo mark, windows tight above 30 mph, etc.?

Tire Pressure:
I have experimented with tire pressures ranging from 35 to 60 PSI. I have found that there is not a measurable difference in FE at higher speeds (42 MPH or above), but that one can increase FE at lower speeds by two to three percent with 60 PSI compared to 35 PSI. The increase seams to be linear between 35 and 60 so I have settled on 50 PSI. I expect that this would give me a two percent advantage at lower speeds (Below 42 MPH) over those who run the recommended 35 PSI. These figures are based on the OEM Goodyear Integrity Tires.

Tire Break-in:
I have also recorded a significant increase in lower speed FE between new OEM tires and worn out (2/32nd tread depth) OEM Tires. The worn out tires, even after correcting for the smaller circumference due to reduced tread depth (approx 0.6% overstatement in FE), can outperform new OEM tires by 3-5% at 60 PSI. This would suggest that the rolling resistance of tires decrease as they are broken in.

Oil:
I use 0W-20 Mobil 1 Synthetic oil filled to the halfway mark between the hi/lo mark. However, I don’t have any good data that would suggest a benefit over 5W-30 conventional oil. I change my oil and filter every 15,000 miles. My next change is coming up soon, but since the 0W-20 is no longer available, I will have to settle for the 5W-20 Mobil 1.

Wayne wrote:
Are there any tips/tricks on using Max Fan w/out A/C in a Prius II for summer temp hypermiling?

Climate Control:
At higher speeds, my windows are shut tight. I use the fan until the interior temp gets up to about 83F. Above that I use AC set to 83F. At lower speeds I have the drivers front window open 3” and the passenger side rear window open 3”. This creates a nice cross flow. If that is not enough to keep me comfortable I use the fan. I do not use AC at lower speeds. During the colder months I wear a heavy coat, a hat and gloves. I rarely use the heater unless the outside temps get into the teens and 20’s.

Wayne wrote:
How about acceleration? Fast but smooth enough to get the ICE up and running from launch, slow crawl up to cruising speed via EV with a smooth transition into the ICE, or something in between? I have also read about attempting to keep a Prius II’s HSD from Regen as well as Propulsion when attempting a long coast to a stop. It sounds as if you use the energy flow screen as feedback to guide a very light touch of the accelerator when coasting to keep regen/propulsion at bay? Do you use a similar technique in your Prius or are your travels more conducive to other, less intrusive FE techniques?

Driving Style:
I have two distinct driving styles, which I will call standard and hyper mode.

Standard Mode:
Mostly I use the standard mode because it doesn’t take much effort. On the highway, I just set cruise control to 55 MPH and go. In city driving, during acceleration or maintaining speed uphill, I use the deadband technique. This means no flow to or from the battery while accelerating. I glide (no flow at all, ICE is stopped) during mild downhill stretches. I apply the brakes (regen) on steeper downhill stretches to keep my speed below 42MPH. When coming to a stop I coast (foot off the accelerator) to stops. While braking and coasting a small amount of regen is provided to maintain the battery level. Standard mode yields the FE data that I provided earlier. I use this technique on my daily commute which is 50% highway at 55MPH and 50% city at 35 MPH. Depending on environmental variables, during the summer my FE ranges from 67 to 72 MPG.

Hyper Mode:
Occasionally I have an opportunity to use hyper mode. The key to hyper mode is the “pulse and glide” technique. The main goal behind “pulse and glide” is to minimize energy conversion. Energy conversion occurs when you convert fuel into kinetic energy, when you store kinetic energy as potential energy (charging the battery), and when you convert potential energy back into kinetic energy (discharging the battery). Each conversion results in losses. It is estimated that the ICE is only about 35% efficient, and that charging and discharging the battery is 80-90% efficient. In general, the energy losses manifest themselves as heat.

The “pulse and glide” technique seeks to minimize the amount of time that the ICE runs, and minimize power flowing to and from the battery. The “pulse” refers to deadband acceleration (no flow to or from the battery) up to 40 MPH. Next comes the “glide” (ICE is stopped, no flow at all) where the speed slowly decreases to 33 MPH. The cycle continues until a stop is required, at such time the brakes are applied and some regen helps to maintain the battery level. Brakes are also applied if a downhill stretch causes the speed to exceed 40MPH.

On level roads, the rate of acceleration will be about equal to the rate of deceleration. That would suggest that the ICE will run approx 50% of the time. So the FE would be twice as much as the FE indicated during acceleration. I have recorded FE in the low 90’s on level roads.

Contrary to popular belief, a route with gently rolling hills can increase FE. This is because the “pulse” happens when climbing the hill and the “glide” happens during the descent. The FE will be lower while climbing but the “glide” will last much longer. On some routes, during “pulse and glide” the ICE need only run about 25% of the time, yielding a FE four times as much as the FE indicated while climbing the hill. I have recorded FE over 100MPG (estimated at over 104 for over 100 miles) on a route with gently rolling hills.

In some situations, the pulse technique might require modification if there is not enough regen (stop lights, braking to maintain 40 MPH down hill) to maintain the battery level. Even though “pulse and glide” does not use the battery to propel the car, battery power is required to start the ICE at the beginning of each “pulse”. Likewise, battery power is required to power the electrical systems (estimated at 600W continuous). If you notice the battery level dropping to 4 bars, change the “pulse” technique from “deadband acceleration” to “charging acceleration”. This is a slightly slower rate of acceleration where the ICE also charges the battery. The FE during acceleration is about the same but the ICE runs longer, so FE will decrease until your battery level recovers to 5 bars. If your battery gets below 4 bars, it is nearly impossible to glide (deadband), as the ICE will want to charge the battery.

Wayne wrote:
I remember reading how you love cruise but have never read that you have “Driven w/ Load”? I ask this because I remember reading how a Graham Scanner helped Rick Reese nail down a 70 + mpg tank in his Prius I using that technique.

I don’t understand what is meant by “Driven w/Load”. Can you elaborate?

Wayne wrote:
___I have so little experience with the HSD/eCVT based automobiles and you just never know when this kind of knowledge could come in handy.

I hope this helps! Now, can someone give me a similar tutorial on IMA? I wonder if "pulse and glide" would work well for IMA and if gently rolling hills are preferable to level roads.

Re: Magic Numbers for Max FE?
 

For the benefit of all Prius owners, Krousdb's previous post has some excellent tips on maximizing fuel economy in your cars.

Seems like it would make a great article to add to the "Learn" section.

Regards,

Re: Magic Numbers for Max FE?
 

Sweet spots for HSD differ by terrain and conditions.

That's not a fact, but merely my impression, I simply wanted to summarize the posting in the first sentence.
Just like everyone else here I have been interested in speed vs mileage relationships for my 05 Prius II, but I've come to the conclusion that there is no single relationship that can describe optimal efficiency vs speed, for all conditions.
In addition, while theoretically it is correct that the faster you drive, the greater the drag and the lower your mileage, there are instances where I believe that is simply not true for HSD, where if under identical conditions you would drive slower, your mileage would go down. My guess is that it relates to the programming of HSD operations, in terms of cycling of HSD components, and loading of ICE via generator, etc..
The reason I believe that is the case is my experiences driving in TX hill country. Specifically, the trip from Fredericksburg to Enchanted Rock State Park, about 16 miles one way, over hilly terrain, with altitude change. Repeated trips back and forth revealed (round trips!) that under identical conditions, if I drove around 50 mph, mileage would be well below 50, closer to 45 in fact, but if I stayed above 60 and closer to 65 mph, mileage jumped to 65 to 70 mpg!
The only way I can explain that relates to the specific nature of the hilly terrain: short but steep hills, up and down, up and down. At slower speeds, the ICE labors on the uphill, and instantaneous mileage is almost down to 10. Coasting down the other side it is high, but not always 99, since the ICE needs to charge the batteries depleted on the climbs. At a higher speeds, since the hills are steep but very short, I can ease up the inclines by starting at high speed and 'coasting' uphill while rapidly deceleration, and then accelerating on the downhills, and maintaining an overall high level of instantaneous mileage.
(see also the very informative post above by krousdb)
On a level highway, things obviously are different, but there may still be some similar factors at work. Traffic makes a big difference in terms of coasting or drafting. While this may sound silly, I have the distinct impression that when driving fast on a highway in a fairly dense group of cars, HSD benefits from the drafting effect of the combined traffic around you, and my mileage is much better than when driving the same strech of highway at the same speed without any traffic. In addition to the drafting effect though, I suspect the HSD is more efficient (in my experience) when not driving constant, but when continuously varying speed.
The same strech of highway I often drive at more or less the same speed (around65-70), I have gotten mileage as low as 42, and as high as 65, at different times, and my impression is that fast flowing traffic with not very constant speed increases mileage, while absence of any traffic, constant speed, and lower temperatures decrease mileage. Headwind also makes a huge difference (in our coastal regions).
I have also nopticed what others posted (based on instantaneous mileage readout), that under certain conditions driving for 15 - 20 minutes at 65 I get worse mileage than driving 15-20 minutes under the same conditions, at 68. However, the optimal speed for best mileage differes on conditions, and when there is little or no traffic, then optimal speed is lower than 65.
To date, I have mostly driven with the help of the consumption screen with the 5-minute avg mileage display, trying to adjust my driving to conditions in order to maximize these 5-min bars.
I really like the idea of krousdb of using the energy flow screen to minimize energy flow to/from battery although I'm not quite sure yet if I can wrap my head around that in an intellectual way:
while I understand that energy flow to/from the battery could be considered wasteful because of the low conversion efficiency, such flow at the same time increases overall HSD efficiency to some extent, by optimizing the load on the ICE and thus raising the thermodynamic efficiency of the ICE.
My guess is that this is precisely what Toyota engineers mapped for the programming of HSD, when to use a given amount of energy flow to/from battery, in order to maximize thermodynamic ICE efficiency and thus help improve HSD efficiency, and that is also why I believe HSD has sweet spots that differ for varying conditions.

Re: Magic Numbers for Max FE?
 

Hi Krousdb:

___That was the best HSD hypermileage tutorial I have ever had the opportunity to read to date and I want to personally thank you for it. I had only a foggy idea as to what was going on in the HSD at or around 42 mph and you cleared a lot of my and I am sure others misconceptions up. I can only hope Jason makes your post and his thread a sticky. Actually, he could use the help in his Prius II ;)

___I hope the following helps you in regards to IMA, hypermileage, and my experiences with it.

Tire Pressure’s: I ran pressures of 60 # for the record setters in the RE92’s and I would drop back to 52 - 56 #’s (normal leak off) for every day commuting.

Tire Break-in: Same thing with Insight’s RE92’s although I never had the opportunity to see 4 brand new RE92’s on my own at the same time. According to others that have replaced them with like for like, it is an ~ 3,000 mile penalty before they open up for maximum FE once again although no one has ever scientifically measured the actual FE delta from new on up that I have read?

Oil: Mobil1 0W-20 was its staple as it is in the rest of my automobiles. I horded a few cases so I have ~ 5 years worth for the Accord ;)

___The following may be of some interest to you?

Kinematic Viscosities (ASTM D-445) of the respective manufacturer’s synthetic oils:

Mobil1 SAE 0W-20
cSt @ 40 degrees C = 43.0
cSt @ 100 degrees C = 8.4

Pennzoil SAE 0W-20
cSt @ 40 degrees C = 46.5
cSt @ 100 degrees C = 8.7

Mobil1 SAE 5W-20
cSt @ 40 degrees C = 48.3
cSt @ 100 degrees C = 8.8

Amsoil SAE 5W-20
cSt @ 40 degrees C = 49.6
cSt @ 100 degrees C = 9.0

Climate Control: Buttoned up tight at speeds > 30 mph. Two windows open from a stop to ~ the same 30 mph. Max Fan w A/C disengaged. Spray bottle and ice cooler on the 90 + degree days. This is where the Prius has me at a loss. Can you run max fan flow from the vents w/out A/C? I thought I remember reading that you could not?

Driving style:

Std. Hypermileage Mode: Accelerations held to just below or just into 4 bars of assist and backing off to remove them (IMA’s std. engagement and tough to keep out of in second gear) appeared to allow the highest FE over a given distance during accelerations. There was no forced or hidden charge hit later on to bring your overall down. This is slow and steady up from 1st all the way through 5th. Once in 5th w/ lean-burn, you would “drive with load” to maintain it. That is slowly decelerating on any uphill climb to maintain lean burn and slowly accelerating on the down slopes back to the target speed if there was no delta between initial and final elevations. This works very well with the non-hybrid’s too. Speeds ranged from 50 - 67 mph depending on the down slopes length and grade. Maintaining a relatively steady band between 45 - 54 mph on the flats would leave you highway legal but just barely. This was good for a usual 95 - 117 mpg depending on wind conditions in warmer late spring, summer, and early fall temps here in Northern Illinois.

Extreme Hypermileage Mode: Same accelerations and techniques but slower overall speeds. The record runs came about at 33 (DWL speed at crests) - 48 min/max speeds and driving at the absolute minimums out on rural highways. When driving locally, 33 - 35 mph at just above idle would give a relatively steady 125 - 135 mpg but local roads are not conducive for this over a longer period given the lights, signs, and traffic to kill off momentum.

___Pulse and Glide with an IMA is not quite the same as your description for the Prius II. The following works for max FE also but it depends on traffic conditions. The Insight with a quick 1 - 2 - and maybe even into 3rd w/out assist and forced autostop for a long coast afterwards would yield excellent results but traffic jams are never conducive to let the glide continue to a stop nor was it practical over a given distance. I experimented with 1- 2 - 3 - forced autostops and coast to an actual stop on a country road out near my workplace late last year. With that, I could maintain 140 mpg over 5 miles but it wasn’t practical to coast all the way to a stop after each pulse. In heavy traffic using maximum buffers, pulse and glide was all I had and with it, I could maintain > 100 mpg but because there is never a uniform gap opening up in any acceleration phase nor regular distance before you actually did have to grab some regen nor heaven forbid, use the mechanicals, I could only very rarely increase my p[resent FE in the heaviest of traffic. It was a lot of work to simply maintain the current FE so I disliked driving under those conditions as do most for the more normal obvious “I hate traffic jams” reason.

___The pulse and glide technique that you described with the Prius II would not help the IMA equipped Honda’s imho because the ICE doesn’t shut down. That is unless through a forced autostop. Very few IMA or non-hybrid drivers use Forced Autostops to maximize FE but in heavy and still moving traffic, it is most certainly available for those with a stick in particular.

Gently rolling hills were never conducive to maximums with an IMA equipped hybrid in my experience. The flats at the lowest RPM’s and in the highest gear were however.

___And something extra … Straight drafts were relatively useless in the Insight because she really didn’t have the power at maximum FE (maintaining Lean Burn in fifth) to keep up with the continuous ebb and flow of the target when attempting to maintain a proper close in. When you did find an 18-wheeler at a steady 45 - 48 mph on just the right section of roadway for whatever reason, you could peg the instantaneous at 150 mpg for however long the steady pace was maintained. Only on relatively flat terrain however. Traffic side drafts were the Insight’s godsend. Because of the slower speeds in the far right lanes vs. those in the middle and left lanes, the delta would help push her into a healthy average even when there was a headwind up to a max of maybe 10 mph. Out in the open with a headwind, maximum FE was very painful to achieve. As wind speeds climbed, this would become maddening until you were at a point when you needed 3rd gear just to maintain highway speed. I do not know if you have ever driven in a 30 + mph headwind in the Prius II yet but from my experience in the Insight, you do not want to do this … ever ;)

___Good Luck

___Wayne R. Gerdes
___Waynegerdes@earthlink.net

Re: Magic Numbers for Max FE?
 

Thanks everyone for the kind feedback and thanks to Wayne for the IMA turorial. I understand conceptually, but because I have never driven a Honda Hybrid, I am foggy on a few things. But maybe you can show me in person the next time I visit my parents in Aurora, IL. How far are you from there?

With regard to the fan, i have never tried the highest setting but I have run it one notch lower than high without requiring the AC. When you first turn on the fan, AC comes on automatically. All you have to do is turn off the AC and the fan will continue to run. Great idea about the spray bottle and ice. I will try that some time.

Re: Magic Numbers for Max FE?
 

Hi MGBGT:

___The wind tunnel effect as you mentioned is a traffic side draft.

___For that continual climb/descent route you described, about all I can add is I hope you would attempt a DWL technique through that area. Steady speeds are FE killers in the hills in my experience.

___Finally, to give everyone a heads up as to Krousdb’s accomplishments, he has taken his Prius II for a max tank range of 967 miles at almost 86 mpg. This is in a NA spec’ed Prius II with the smaller bladdered tank, not the non-PZEV Japanese version with the much larger cap. I hope most are cognizant of what it takes to achieve this level of FE in a Prius II as well as how important his comments are for those interested in taking their Prius’ or any HSD/eCVT based hybrid’s to their limits.

___Krousdb, Aurora, IL.? I drive by that city every day! If you are ever in the area, drop me a PM as I would love to meet up with another hybrid/FE enthusiast. Although I do not own an Insight anymore, the same basic techniques work in the Accord, Ranger, Corolla, and MDX. If you happen to be in or around the area on July 17, you will have to come with us to the Wi./Il. hybrid group meet to see the Milwaukee Brewer’s at Miller Park up north in Milwaukee. There are a more then a few hypermiler’s scheduled to appear again this year and Ericbecky puts on a pretty nice show for all that attend ;)

___Good Luck

___Wayne R. Gerdes
___Waynegerdes@earthlink.net

Re: Magic Numbers for Max FE?
 

Thanks for the invite but that is a bad weekend for me. Keep me in mind for the next one.