Quote:
Originally Posted by mattebury
Unless you put in exactly the same amount of fuel as when you started, you will always be off from the dash computer. I know people say that their hand calculations are more accurate, but unless you have a visible calibration line set on your fuel tank to prove that you always start with the same amount of fuel, I'd expect my numbers to be different from what I pumped into the tank and what the dash computer is telling me. On a 300 mile trip, with the dash indicating 10 MPG which should be 30 gallons, a one gallon difference in what you actually pump into the tank and your hand calculated mileage could be as high as 10.3 (pumping 29 gallons) and as low as 9.7 (pumping 31 gallons).
Since the tank is opaque, it's impossible to tell after you fill-up, you have exactly the same amount of fuel as your last fill.
|
as indicated in my post: "fillups were to the brim" I have been doing this since 1995 with my diesel trucks.
Liquid fuel about 1 inch below the filler cap opening; with a wait to insure no more air coming up with resulting settling. Same pump at the same fuel station too.
Maybe I bought fuel after a 'hot' unload at the beginning of the trip.
I have records comparing dash display to the actual MPG all the way back to the 04 and 06 trucks and have never had it that far off and I use to buy fuel at a station accussed by a big rig trucking magazine of selling 'hot' fuel.
Hot fuel is unlikely.... Not likely someone stole any either or why not take more? Subseqent tanks are back to fairly close so not likely I have an injector leaking either.
The difference is more than a gallon; even if assuming the display was .6 MPG too high and knocking it down from 16.4 to 15.8; 475.6 mi/15.8mpg = 30.101 gal; or 2.319 gallons less than I purchased.
Maybe I reset the thing and didn't realize it; or remember since that (my memory) seems to be going with age
Bob
