Hey Guys,

Could any of you shed some light on how the car calculates the MPG? I was in a rush to the dealership on Friday, so I only filled up the tank half-way. When I looked at the calculated mpg in the afternoon, it was at 11.6 and slowly rising (and I do mean slowly). I'm thinking everytime you refuel, the mpg calculator assumes it's a full tank. Thoughts?

 

What was the "Range" figure it gave you? If the computer was assuming a full tank then that would also indicate incorrectly at somewhere around 350 miles.

 

I've only filled the tank completely but the tank average seems to be right on. I just did 380 miles on one tank in our GS430. The "Tank Average" said 26.0 mpg and when I filled it up it came to 26.09 mpg

 

It takes the average of whatever it was the last time gas was put into the tank. Even if it's .001 gallons, it'll still reset it.