jb904

my 98 ls400 had its check engine light come on. I havent been able to find out what it means just yet but since its been on i havent noticed any change in how the car drives. i drive in the city but im easy on the pedal driving like granny and my display is showing 20 mpg average. however after filling up my car recently i did the math (total miles driven/gallons filled) and the actual mpg is 14. If my display is somehow off how would i fix that? Or is it a chance that the check engine light is causing the misread for the MPG?

selkirk

The average calculation is calculated since it was last reset - did you reset it when you filled the car up last time?

If you reset it partway through this tank, or if you last reset it a few tanks (or more?) ago and did some highway driving since then, that will influence the average it tells you.