Been suspecting and recently confirmed on my 1995 F-150 extra cab with long bed, 302, auto:
8.5 mpg out of rear tank, and
13.0 mpg out of front tank.
Both tanks computed while other tank was full.
Any hints?
thanks,,,,,,,,,,steve in California

 

The tanks are not the same size, the front tank is a little bit larger than the rear tank, so that could affect your calculations. If you are already aware of this and have adjusted your calculations accordingly, then I am not sure what would cause the difference.

 

Front tank is 19 gals, rear tank is 17 gals, NEVER run them dry, it will heat up the integral fuel pump and eventually cause its replacement.
I figure MPG by miles driven by gallons required to fill up tank, tank capacity is inconsequential.

 

The tank with the higher mileage might have a bad fuel pump, I would check the fuel pressure of each tank

 

clogged fuel filter perhaps? Do you notice a performance difference between tanks? That is an interesting problem!

 

Interesting note on fuel mileage. I have a hobby of keeping track of every tank of gas and figuring the mileage on paper on my 2010 Supercrew cab 4X4. Lately I noticed that the mileage had dropped. I checked the tire pressure and they were at 34 pounds. So I pumped them up to 40 pounds, 5 pounds over recommended. My mileage immediately increased by over 2 miles per gallon to 18.9 on my regular 300 mile weekly trip. My in truck mileage gauge hit 21.8 mpg, higher then I had ever seen it.

 

O.K., major service, all fluids/filters, one O2 sensor, etc. changed, new plugs/wires, rotor, dist. cap, etc.
Will be filling up soon and computing new mileage. Bed (w/cab high shell) is still heavily laden-- so mileage can compare before service..................................steve
still open to more suggestions

 

deerhunter,
I used to play with tire pressures also. You are correct, mileage will inrease with less rolling resistance (higher p.s.i.), but watch for uneven tire wear=in the center of tire if psi too high, on the outer edges if psi too low.

 

I just put new tires on my truck. Drove it 300 miles with the tires at 40 pounds and only got 16.4. So I noticed on the tires, 45 pound maximum. So I pumped them up to 44 pounds.

I am now on a 6000 mile trip to the west coast. On the first tank, I drove 610 miles and got 19.4 mpg. The nice thing was with the 36 gallon tank, I was able to make it to Missouri and bought gasoline at 2.959. Will fill it up completely before I leave this state as I hear the rest of the western states have prices much higher

So watching and experimenting with your tire pressure can produce good results. I am aware of the possibility of increased tire wear and poorer traction with over inflated tires.

 

I have a new 2011 fx4 5.0 just over 5k on it,and I'm only getting 12 to 13 miles to the gal tires pumped up city driving on a counter and on b over all.