Thread: better gas mileage when tank is full/almost full

car companies have been doing this for a long long time. The gauge moves very slowly at first. its said to give the impression the car gets better mileage then it really does. Its documented in a few places. Oddly enough my 92 pickup was FAR worse then my 06 GP. I'd go 100 miles without the gauge moving and then all of a sudden it'd start dropping like a rock.

In reality if anything, your car gets better mileage with less fuel in the tank due to weight.

I don't know about the GP, but a lot of times it's due to the shape of the tank. The closer it is the being "V" shaped the more you'll notice the guage accelerating as it gets closer to empty. Technically you'll get better gas milage the less gas you have (i.e. less weight).

GM gauges read funny? Tell me it ain't so!