I thought I'd seen something on this, but I cannot find the thread.

I've tracked the fuel economy of my FEH since the day it was new. I'd made a spreadsheet for which the dominant columns are the odometer reading and the gallons of fuel that I added at that fillup (I track more, but these two columns are used for all the calculations that I use). Though I do track the milage that the computer says I got, I never paid much attention to comparing it until this last fillup.

My computer shows that I got 32.2 MPG on this tank. My spreadsheet shows that I got 30.85. I guess it caught my eye because I was happy to have gotten better than 32 and was shocked that the spreadsheet showed a number starting with 30. In my mind that's a 2mpg difference (even though it's really only 1.35mpg).

I started to try to think about the difference and why the discrepancy would be so much. What I did next was just tweak the spreadsheet by reporting that I put in just a little less gas.

On each tank I usually just let the pump run until it cuts off. Occasionally I'll try to add a few drops of gasoline to round off to the next even dollar amount. I've started to realize that this causes me to vary a "fillup" by as much as 1/2 gallon.

Turns out that 1/2 gallon makes all the difference (esp. when you put in less than 12 gallons on average). If I back out just 1/2 gallon from my fillup, my fuel economy reports 32.21mpg (which is pretty much exactly what the car's computer reported).

In the long run this might negatively report a tank (make it look like I'm getting worse economy than I really am), but it should average out -- I should occasionally get tanks that appear to be much better than the computer reported. I'll have to pay closer attention at the pump and see if this works out to be the case.

 

Yep, that's what I noticed too, since I don't always put the same amount back in, I can get some pretty weird numbers that way, and though the display may not be dead accurate, it does seem to be pretty darn close for the most part.

 

I reset my average MPG display and set out to become a hypermiler. I didn't really think I could do it because I drive 60 miles each way to work (the reason I got a hybrid). The route is not at all flat and I have 40 miles of highway (which has quite a few long hills in and out of the river valleys. The rest is a mix of city and secondary roads. I got the 4WD version since we get some pretty bad storms here so I pay for that with gas milage.

Anyway, one full round trip and a little extra and I'm at 31.6MPG. Not too bad for a newbie and having it less than a month. I did drive pretty conservatively and mostly stayed in the right lane on the highway, but I also didn't crawl away from the stop lights if someone was behind me. I know I can do better!

I'm not really addicted, I can stop any time. Really.

 

It really does vary a lot depending on your fillup consistency. In Oregon we don't have self-serve so I have very limited control over it. I can tell you that since I've been tracking it (2/17/05), the maximum delta between computer estimate and my hand-calculation has been 2.36 MPG but the overall average delta is only 0.49 MPG.