We picked up our 2008 FEH last Saturday. Did a lot of research on this board and others about how to get the best fuel efficiency and have done pretty well so far -- we're at nearly 32 mpg after just about 200 miles. But as a newbie in the FEH world, I've got a couple of questions -- and I'm sure others will have their own. So thought I'd start this thread with two questions:

1) One thing that does wonders for our FE is driving in L while in the city (which is probably 60% of our typical daily driving). I learned about this from the FAQ and various other postings -- but noted that they were all a couple of years old. And most had something of a "seems like a good idea but we're not sure whether this is OK in the long-run" slant to them. Has anyone gotten any official word from Ford -- or good advice from engineers or others likely to know -- about whether regular driving in L is a good idea, or whether there are any major downsides? I emailed Ford and asked this question, but so far haven't gotten anything useful out of them. Would like to be sure that I'm not doing major damage to the car while saving gas!

2) Also want to verify what the average mpg gauge is actually measuring. Can I assume that (unless you reset it) it's reading average mpg on the current tank of gas? I've read the Owner's Manual from cover to cover but there's no explanation of what this gauge is actually measuring (could be mpg at this particular second or from the beginning of driving history, etc.).

I'm sure to be back with more questions. You guys are great! We're looking for many miles in the new FEH. As an indication of just how unfashionable we are (I prefer to think "counter-cultural"), our FEH is blue -- the least popular color -- and has no NAV or other options.

Liz

 

Avg MPG hasn't exactly been sorted out. The official word is that it is, like the last 1,000 data points stored in the system. However, no one has gotten clarification as to what or when the data points are recorded. Most people just reset it with each fill up. The MPG display also seems to be about 2mpg inflated over MPG calculated by "hand". My display often shows the tank average at 30mpg, but based on my calculations my true average is closer to 28mpg.

 

Hello, and welcome to GH.

As to your questions:

1. At the FEH Experience in Dearborn, we did get an absolute answer, and it should be in the FAQ as such. The FEH runs on "Drive By Wire", which means that shift column your playing with isn't actually a physical selector. It tells the computers what you'd like it to do, which if reasonable, it does. You can shift that thing all day long, and it won't make a difference, especially between D and L, since that's entirely a programming change, not a physical one.

2. That ones a bit harder to answer. It is the last 2000 data points collected, but we've had a difficult time getting just what those last 2000 are. However, if you reset it with each tank, it'll be a good estimate of your MPGs. You may find, as Tim does, that it reads high, but we've gotten a mix, from 2 MPG high to 3 MPG low, so you'll have to see for yourself. (I've had it both ways incidently, and spot on many times.)

 

I think the NAV may be more accurate than some think. The problem is with "manual calculation".

I've got a ScanGuage II and you are supposed to make an adjustment on it during your fillups to ensure its accuracy. The adjustment consists of using the same pump to fill the tank twice, and then looking at the amount of gas used and checking it with the readout on the gas pump. I've done this several times (like 10 or more). Frankly, using the same pump, on the first automatic shutoff, the results are NOT VERY CONSISTENT! I've even tried a different pump to see if it would be more consistent. I've ended up with adjustment % numbers on the ScanGuage everywhere from 4% to over 10%. 6% seems to be the most common... and strangely, when I use about 6%, the ScanGuage reads pretty much in line with my NAV about +/- 0.5MPG (until I get a few days into a tank and I'm past the 2000 points).

 

I don't have the Scan Gauge. I just use the mpg readout on the NAV system. I reset it every fill up and usually wait until I'm on E to fill up. I've noticed that since I bought my current FEH (an '07 which I purchased in August of '06), the mpg readout has been getting more accurate. On the drive home from the dealership the first day, it said I got something like 47mpg for my roughly 15 mile city drive. That was definitely way too high. It started getting more and more accurate as I had more fillups, but sort of leveled off at being 2mpg higher that what I calculated each time. That is until my last 3 fillups. They have been spot on.

I owned an '05 FEH for about a year before I traded it in for my '07. It was spot on almost every time.

I think a major factor that it comes down to is when you stop pumping gas into your tank. Do you "top it off" after the first time the pump clicks off or not? I don't know the "correct" answer, but I would guess that being consistent (either always or never topping it off and using the same gas pump) would give you the most accurate results. As to whether that would help the hand calculations match up to the readout, I don't know.

 

I almost always wait until my miles-to-empty is at or near zero. And when I fill up, I almost always put between 13.6-13.9 gallons in. I would say that about 75% of my fillups fall into this range. I've only had the NAV run high 5 times and be on par with the manual number about twice. I don't think that leaves much room for error over the course of 30

 

When I'm setting up the calibration for the scanguage I follow its instructions which are to let the pump click off automatically and do not top off.

 

I just wanted to make sure it's okay to shift between "D" and "L" while your foot is pressing down on the gas pedal. I'm used to a manual transmission and letting my foot off the gas before shifting.

 

Since it's electronically controlled, that shouldn't hurt anything. I don't think the computer will let you do anything to harm it. The only thing shifting to L changes is the regenerative breaking strategy, and that's entirely computer controlled. It feels no different while accelerating until you let off the gas. I usually do it the other way, shifting from L to D while stepping on the gas and only use L to break and regen.

 

Yes, it is. In fact, if you want to really freak someone out (I don't really advocate doing this, but you can,) drive down a road, maintain a constant 40 MPH, then throw it into reverse.

You'll keep going, because the PCM sees that as an unreasonable request and won't shift into R until it slows down, at which point it becomes a reasonable request and then will comply and shift you into reverse. The vehicle won't do anything that's not safe for it to do, and will ignore any unreasonable requests from the driver, which is all the shift column is. (Performance wise, I'm not saying it won't drive into a wall) Or, as I say, the car is a lot smarter than most people.

Once again, the only difference between L and D is a software change, there's no physical one, and the computer doesn't mind at all, as the only difference really is the automatic light breaking in L.

This is from the mouth of the person who designed, developed, and tested the system. I don't think there's anyone on Earth who would know better.