So when I do my averages I should divide by 13 gallons instead of 17.1? Does the fuel gauge go by 17 gallons or by the 13 gallons? Thanks, only reason I'm curious is because it always seemed like I was getting low mileage and I thought it was a problem.

 

Basic math, tanks size doesn't matter.

Fill your tank. Note the miles on the odometer. Drive.
Next fill up subtract your previous odo reading from the current reading. Divide that number by the amount of gas you just bought. That is your MPG.
Repeat process.

 

Yea I get that part, what I mean is does the fuel gauge read the full 17 gallons, or about 13? (When the gauge is at the half tank marker does it mean 8.5 gallons left, or 6.5 gallons left?) Thanks

 

The fuel gauge is really not an accurate thing to look at. For instance when I have a full tank my needle is well above the full mark and won't move at all for the first 100-120 miles. From full to 3/4 tank takes another 100 miles or so. From 3/4 to 1/4 might be another 120 miles. The only thing that is constant at all with my fuel gauge is that when my fuel light comes on I have about 3.7-4 gallons left.

If you want to benchmark it you will need to do something like fillup when your needle hits 1/2 tank and note how much fuel it took. Then do that again, at the same place on the needle and get kind of a ballpark figure of what 1/2 tank on the gauge really is in gallons.

To answer the basic question here, Full = 17.3 gallons. I doubt that 1/2 will be 8.65. On mine 1/2 is actually about 10 gallons used.