Computer average vs. ACTUAL MPG - DISCREPENCY!!!

[ITEM9]

Originally Posted by lexicon

Oh, OK - lol.
The amount the pump measured out should be very accurate, although I guess there's always a chance it went faulty.
What I meant was, it's more likely that you didn't get the same level of fill in the car - as sirjonsnow said, the cutoff works off changes in air pressure and can be affected by all sorts, so the first click could vary by quite a bit even on the same pump.
And, because our tank is small, it won't take much to throw the numbers a way out.
I usually fill to click, wait a few seconds for it to settle, then fill to click again but I still see variation.

Exactly. Fortunately, this type of error can be minimized by logging your fill ups and looking at the average over a few tanks. The more tanks you average together, the less this error becomes.

[Mr. Incandenza]

Just wanted to chime in and say that unless you're filling to the top, even at the same pump, you're going to get variance. From what I've seen so far, this is the most accurate MPG meter I've ever seen in a car. Sometimes it reports a little low, but we're talking .5mpg +/-. So I'd pin it on shaky source data (pump stopped at a different level).

[Noodles]

I’ve measured mileage in 11 tanks and compared it to the computer. My measurements varied from 0.55 mpg lower to 0.2 mpg higher than the computer. So far, on average my numbers are 0.16 mpg lower than the computer.

[Klasse Act]

My OBC is usually spot on or at the worst case, about 1 mpg optimistic, that's it and now that I'm on Fuelly, it does the manual calculations for me, along with everything else. Now OP, your mileage is below what most of us get, what's your driving style like?

[gearhead313]

Well its good to hear that other people are not having my problem. ill keep logging and see what i come up with