Originally Posted by Knightrider03m
Even driving 30 miles on the freeway and filling it back up, my computer was wrong.
How did you know you got the exact amount of fuel in the tank for the 30 mile run, same fuel temp, same gas station, same altitude. Just a little bit of deviation makes a big discrepancy. How do you know the EVIC is using the same ground rules? I always get a kick out of the misinformed and sloppy data collectors trying to justify what they see, or just seeing what the want.
Tank to tank fuel usage calculations are only good for long term trending. Trying to do a relatively instantaneous measurement with valid results is useless.
Now the EVIC will tell you how much fuel the computer thought it squirted into the cylinders over the distance, but it is not going to notice anything extra getting by the injectors. So more likely than not it will be optimistic. Its useful, however, as feedback to what driving styles provide the best mpg.