As many of you know, I'm both vocal and fickle with my ascertions regarding what my FE is.

After driving for an entire tank trying to keep my FE above 42 and only succeeding to keep it at 41.1 (computed), I've noticed that you can gain and lose MPG when fewer miles on the computed miles per tank than with more. So, for example, once I exceed 200 miles on the tank, its both harder to increase the MPG and harder to decrease it with unlimited accelerations. Once I reach 350 miles per the tank basically I neither gain nor lose MPG (well, I can very easily lose it but nearly never make it back).

Witness yeserday. On a computed 41.1 MPG tank at 457 miles I figured that to be about 11 gallons (but I know that my computed MPG is *always* 1.8 MPG lower than calculated at the pump). So, I decided to be mister Careful and see if I can make a 42 mile journey home and through the hills and endless stop signals without filling up.j I drove even more than that on other out-of-the-ways totaling 70 some odd miles.

I was so careful that I actually increased my MPG to 46 MPG in just 40 miles, something I've never done in my life that close to the end of the tank. I ended up driving 530 miles on that tank of gas and filling up at the pump 11.32 gallons of gas.

So my point here, is that, even though in my 8,400 miles of driving this thing, I've never before been able to increase my MPG after the 350 mile mark for a tank, when scared crapless that I'd run out of gas something happened that immediately increased my FE.

Hence, good FE isn't just technical, road-conditional, and technique oriented, but also psycological. Lets see how good I do when I treat every road trip I make as if I have no gas to start with.


Thanks,
Shawn

 

You are precisely correct Shawn, good FE is simply a matter of discipline. As you mentioned, the Instantaneous FE guage and A & B trip computers allow you to see this as it changes.

Again, as you mentioned, obviously the more miles on the trip segment the harder it is to have a net effect on the displayed MPG.


I think that the 2 things that seem to (negatively) affect my mileage the most are 1) cold starts; and 2) the obvious need to be courteous enough to others.

 

Man, that is impressive. Increase from 41 to 46 mpg in the last 70 miles of the tank??? It must have been all downhill with a stiff tailwind.... Seriously, great job.


I am not sure, but I think I just hit my "break-in" (at about 4000 miles). It is hard to tell, since I also just increased my tires to 36 psi AND it has gotten cooler here so my A/C use has dropped significantly. Anyway, I went from averaging 44 mpg pretty consistently to my current tank, in which it looks like I will hit around 47-48 mpg on the same commute. Pretty cool.

 

The amount of downhill is negligable, hardly 5% of the trip. The amount of uphill is probly about 35% of the trip, the rest is flat or seems like it (either minor up/down grades over large distances). There are a fair amount overpasses (rough estimate: 25) but I've learned a thing or two about overpasses:

a) if I'm traveling about 60MPG or higher, then I don't need to accelerate the entire uphill to maintain that speed; it is sufficient for me to simply accelerate from the middle-point to the 70-80% point lightly (3,000 RPM but not greater) and then lift my foot back to "feather" mode, and I've neigther lost-nor-gained MPG at the apex of the hill
b) if I have both inertia and momentum (have been accelerating slowly until the hill and more intensely by the base of the hill) I can take my foot off the gas completely until the apex of the hill and I'll gain MPG (depends on the grade and length of incline but 70% of overpasses in Orange County are sufficient for this trick).
c) never accelerate from the point of the apex of the hill until it becomes flat (unless I necessary to avoid a missile SUV on my tail)

When going up long hills at steep grades (3% - 6%+) from a complete stop:

a) I can sufficiently speed to 50 MPH at 1,500 - 2,100 RPMs and not be significantly slower than the normal accelerating traffic
b) when at the front of the line and many missile SUV's and "hotrods" are "competing" for the first position, accelerating at 2,500 - 3,000 RPMs for about 1/8 mile and then easing off to about 1,800 RPM (my normal "cruising" speed) will usually be sufficient to not get plummeted and still maintain good MPG.
c) doing this trick, I usually start with a fresh tank of gas at the bottom of my hill (7 miles or so of 6% grade uphill and more reds than I can count that unconditionally catch no matter what -- except when speeding which I don't do usually)... starting with a fresh tank and 0 miles on the tank, after 7 miles I can have about 45 - 51 MPG on the tank for the commute but I really have to control myself.

Starting cold seems to be better for me... my car seems to love cold (65* ambient temperator and has no problem accelerating and maintaining good RPM. When its hotter out and has been parked in the sun a while (90* or more) it has very slow acceleration and is harder to maintain good RPM until after about 5 miles or so. Some may dissagree with me but these are just my observations. Sometimes I read and talk backwards without realizing it so perhaps I have this backwards to but I this message has a different point I'd like to stress.


Thanks,
Shawn

 

Let's see,

You drove 457 miles with an average MPG of 41.1. That means you consumed 457/41.1=11.12 gallons of gas that far.

Then you drove another 73 miles, for a total of 530 miles, and filled up 11.32 gallons.

So in the last 73 miles you consumed 0.2 gallons of gas, which makes for 73/0.2 = 365 MPG.

Should I believe that?

Now let's assume, as you noted, that your actual MPG is always 1.8 higher. So at 457 miles your MPG was really 42.9 which means you had used 457/42.9=10.65 gallons of gas.

If so, then in the last 73 miles you consumed 0.67 gallons for an MPG of 109.

Should I believe that?

 

i can push my numbers up by being super conservative toward the end of a trip, as long as the engine is sufficiently warm.

 

Shawn, based on Elan's math, this smells of the 100km mpg restart bug... Have you had your display cluster upgraded or replaced?

 

Yes, you should. In my hch I I was able to sustain 115 or so mpg on a near ideal course. The insight marathon finished up at 168mpg over 2254.4 miles on a tank of gas. Given an intense desire to do everything right and by not having any major obstacles it is quite possible. Granted I doubt anyone will get a 115mpg tank in an HCH soon, but someone could potentially pull off around 109MPG on a 73 mile segment. Also, there may be a bit of fudge factor with the numbers since they are rounded and sometimes those 3rd digits after the decimal point make a difference.

At any rate, ElanC, you should keep an open mind. If you want to seem some truly impressive numbers check out cleanmpg.com. I'm learning a lot from Wayne and the others over there. You might go ballistic over there because the numbers some of those guys are posting are astonishing.

Cryx might have a point too. But even if it was due to the bug, his numbers aren't unbelievable.

 

I've never had anything upgraded or replaced (I was just manafactured in early June) but there is one thing that sometimes happens and I can't put my finger on it: when going down hill and my foot is very lightly touching the gas so as the I-MPG feedback reads somewhere between 90-100 MPG the MPG bars sometimes drop to 0 and I don't yet know whether that effects the computed MPG average but to get my MPG bars back I have to take my foot completely off the gas a few seconds than the problem is solved.

I'm pretty sure the odometer is correct in recording the miles traveled. Regardless whether the computed MPG is correct, I can always compute my gas pumped against miles traveled and its almost always about 1.8 miles higher calculated. But, I still treat the computed MPG as gospel until I do fill the tank up and calculate by hand. I'm trying to inch my way up so I can predict my actual fuel consumed and fill up 12 gallons but I not 12.3. I'm slowly getting there.

Thanks,
Shawn

 

Believe what you want; why would I lie? I'm beginning to think that anything is possible with this car. There's no other car that I know of (non-hybrid) that can get a 15-50 MPH difference based on how you drive it. I'm pretty sure my observations are correct but we'll see. So far I've made 3 trips back and forth from where I live and work and for the first time in 45 days I'm up to 53 MPG average (computed) when usually by this time I'd be on 41 or so. Everytime I drive it the MPG increases. Perhaps I'll get it around 55-60 this time. There are a few miles in the city that I can't avoid that effect things but the freeway always helps.

Since I started this thread, I have the I-MPG reading (for the duration of the freeway drive) 85-100 at speeds of 55-72 MPH. I try to keep it at 63 but it seems easier to maintain higher MPG's at 71-74 MPH in certain parts of the commute where the land is mostly flat or slightly downhill. I use it to my advantage.

So, we'll see when I fill this tank up. In the meantime, believe whatever you want.


Thanks,
Shawn