For the past 4 fillups in a row, my avg mileage display in the console says 19.5mpg, but consistently dividing odometer readings by gallons on the pump, my manual calculation gets to 18.5mpg.

How come? You'd think the ECM just counts the miles and the amount of fuel that passes through the fuel injectors...

 

I would trust the manual calculation over the onboard computer...

 

yea id go with the math its stupid but always right

 

The manual is correct. With a VAGcom you can make a correction in the computer plus or minus 10% IIRC.