Do you get better gas mileage with a full tank of gas or a half tank?

Question

fuel economy

Answer 1

Since a gallon of gas weighs approximately 6 pounds, a 20 gallon fuel tank would be about 60 pounds lighter than a full tank. Every extra 100 pounds of weight reduces your fuel consumption by about 1 MPG. So, you will get better mileage with a half tank, vs full tank, although the difference is rather small.

gasoline has a gravity of around 58 and a weight per gallon of 6.216 pounds per gallon. Premium gasoline may have a gravity of 54, or 6.350 pounds per gallon.

Answer 2

I had a 1994 Plymouth Sundance that seemed to get better mileage when the tank was full. Once it reached 1/2 it burned quicker. Maybe other cars are different.

Answer 3

All things being equal, it should not matter.

If you had an enormous tank(40+ US gallons), you could actually see an MPG increase with half a tank. Your city driving MPG rating is based directly off the driver's driving style, the vehicle design, and the weight/mass of the vehicle and its cargo and passengers.  The amount of difference would be so technically small to make it insignificant.

But continuisly running the tank near empty is not a good idea at all.  Modern fuel injected cars with the fuel pumps mounted in the tank, rely on the fuel to keep the pump from overheating.

Answer 4

HALF BECAUSE OF THE LESS WEIGHT.

Answer 5

Without a doubt, you would get better mileage with half a tank. The reason is that your car would be lighter.