Gas Mileage Computer Readings

My 96 Eagle Vision TSI is equipped with an overhead console that contains,
among other toys, a read out for the average MPG that the car is using and
distance to empty.

In these times of (never ending?) price increases I am wondering how
accurate are the readings I get?

Right now, traveling 20 miles a day (mostly city driving) my 3.5L V6 get 20
MPG.

Which is better then the 18 MPG that the EPA's calculates.

Also, I have notice that depending on how the car was parked (level or on a
small grade) the readings I get after I restart the car are difference then
when the car was running before I parked.

So, should I take the computer's readings with a grain (or bag) of salt?

And is there a way to make sure that the computer's readings is "mostly"
correct?

 

For checking mpg, it's very simple to do: Pick a series of five future
fill ups - call them f0, f1, f2, f3, and f4.

Reset the console average at f0. Record miles driven from f0 thru f4
and gallons to fill up only for f1 thru f4 using the exact same
technique to stop each fill up f0 thru f4 (i.e., slow feed approaching
nozzle click-off point, and repeat slow flow to second click-off of
nozzle, then shut pump off). Doing it over several fill ups will
average out any inconsistencies of the individual fill ups. At f4,
compare the console mpg to your actual average calculated from total
miles traveled ÷ total gallons used for f0 thru f4.

The distance to empty varies with how the car is sitting because one of
the variables used in the calculation is how many gallons remaining in
the tank, which is determined by the float level in the tank (varies
with tilting of the vehicle).

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

Even though there is exactly the same amount of gas in the tank before it
was shut off, you may have been traveling on a slight incline while
traveling and parked on the level when stopped. On an incline, the gas would
'pool' to one end of the tank, giving the float arm the impression that
there was more (or less) as in the tank then when level. The computer, now
reading more )or less) fuel calculates a different distance to empty based
on this reading. Will equal out after you get going. (I noticed the same
thing).