bad gas mileage!

[MUDDING B-3000]

ok well ive been reading all the other post an i cant pin point my problem with bad mileage well in the summer i would barely get 300km to a full tank an now its winter so i got the hubs locked an driving 4x4 sometime an i filled my truck up on saturday an driven 75 km an i almost went throught half a tank of gas. i usually am driving back country roads an not a lot of stop on go, ive changed my air filter, fuel filter, an plugs last week an im stilling getting bad mileage??

any ideas?

 

[Earl43P]

O2 sensors go bad over time and affect fuel mileage.

IAT could be bad, telling the PCM incorrect intake air temperature.

ECT could be bad, telling the PCM the coolant isn't getting to operating temperature (even if it really is).

TPS could be bad, giving an incorrect throttle position to the PCM.

FPR could be bad, putting out max fuel pressure at all times.

Thermostat could be bad, does your temp gage work?

Low tire pressure?

Brake(s) dragging?

Vaccum leak?

Poor compression (bad rings, valves)?

Plugged exhaust?

If you've never replaced the O2 sensors, I'd start by looking at them first. Maybe pull them, inspect them and clean the carbon off with a blowtorch and reinstall (or replace them). They go bad over time and don't always light the CEL if they're putting out a "reasonable to the PCM" signal.

Did you put a different speedo gear on the transmission speed sensor when you installed the 31" tires? If not, you are really travelling further than your ODO says you are....

Start ruling things out....

 

[MUDDING B-3000]

ok finally someone answer thanks alot for telling me all of those thing ill start to rule things out, i dont think the guy i bought the truck off of changed the speed sensor so i kno i am really goin faster then my speedometer, but could that change my odometer that much? like if i only am getting 300 to a tank i might be really getting like 400?

 

[Wicked_Sludge]

you need to correct your mileage for the incorrect speedometer.

you also need to figure out your actual MPG, not miles-per-tank.

 

[BadRancher]

I'm having the same issue. I'm gettin around 11 mpg on my 4x4 with mostly city driving.