Fuel Mileage Checking Oversights

Most filling station gas pumps underregister the gallons to avoid code
enforcement fines. Therefore calibrate the gas pump by pumping gas into a
known calibrated container. This error will falsely increase your
calculated mileage.

Most odometers are wrong. Calibrate that against road markers. An
overregistering odometer like mine will also false increase calculated
mileage.

Road surface conditions, water or snow on roadway, load in car, winds,
grades are variables which affect mileage.

Less critical is temperature and atmospheric pressure, and altitude.

Tire pressure is often overlooked.

The professional mileage contestants pump up their tires to about 60 psi
for optimum mileage. They don't care if the tires blow out. Its the
mileage that counts, dude.

Some of you guys out there think you're getting 35 mpg from your Imperial,
but you aren't because all of the above confuse the issue.

 

Odometer inaccuracy is a serious problem and very common, far more
than people realize. The automakers have a vested interest in making
odometers read a few percent high with all the leasing that is done and
the mileage warranties. See the following rather interesting discussion:

http://truckandbarter.com/mt/archives/2004/06/on_the_accuracy.html

Tire size is more important.

You forgot winterized fuel with a higher alcohol content, thus lower power
from it, mileage on these blends is worse.

It should be noted, however, that MPG rates are most useful in comparing
PAST mileage with CURRENT mileage, as a decrease in mpg indicates
engine trouble. SO most of these factors are equalized out. mpg only
becomes significant when comparing it to other vehicles or against the
federal tested mpg.

Ted

 

I thought summer gas had lower fuel efficiency due to the additives used to
reduce vapor emissions having lower energy content than gasoline. Fortunately
the stations local to me don't use any alcohol, although I don't know how much
longer that will continue. I agree EPA mileage figures aren't accurate, but I
usually can do better than the claimed mileage. Since mileage can change a lot
just due to driving style and type of roads driven, it's probably not reasonable
to boil it down to one number fits all--except for comparison only.