Low MPG

I recently noticed that I seemed to be going through gas pretty quickly and when I calculated my MPG off this last fill up it was 12.8. This is a 2003 extra cab 4wd V6. All city driving, but still that seems crazy low! Is it?

Right before this I had the parking break adjusted and there is a lot less play in the break lever now. Could a mis-adjustment of the parking break cause this?

Other common culprits?

 

Jack up the rear end and spin both wheel to see if it'll spin freely or have drag but this shouldn't cause your mpg to drop much unless you're burning your shoe since the adjustment

 

Clean your Mass Airflow Sensor. Worked wonders for mine!! And it is so easy to do!!

 

My 07 gets 19 around town get a tune up (plugs , air filter , maf sensor cleaning , throttle body cleaning)

 

I'm trying to figure this out with my truck, too. When I got it a year and a half ago, even with the supercharger I was getting a hair under 20mpg on the highway, about 18 average. A year later, I'm averaging 15 now if I'm lucky. Only thing I've added that would affect mileage (to my knowledge) is the roof rack and 2" lift which I understand makes me even less aerodynamic. And sliders which account for some extra weight. But I didn't think it would account for this big of a MPG hit...I feel like something else is up. Had my MAF sensor and spark plugs replaced to no avail, also my fuel filter and fuel pump are new.

Sucks when you live in CA and have to buy premium fuel, fortunately I recently moved about 10 minutes from where I work so I don't feel it quite as badly as I did before. If you figure out the issue let us know, I'd like to try it out myself if it's something I haven't already. I've run plenty of fuel system/injector cleaner through the tank but unsurprisingly it didn't help. Might try getting my injectors cleaned by a shop next.

 

How old is the thermostat? If the engine is running slightly cool the computer will run the engine rich. Best to hook up a scanner and see what temperature the computer is seeing. Should be over 180F and stay there.

 

There are about 1000 different things that affect mpg.

Mass airflow sensor, o2 sensor. All that stuff. Though at least 80% of it is that long skinny pedal under your foot. There are a few threads that go i to that in more detail. Just sesrch around for them.

 

heavier tires I have noticed make quite a bit of difference. Even my friends 2011. He upgraded to a 32" tire in the BFG AT KO. dropped 2mpg just from that. Also - any vehicle gets the worst gas mileage on your short commutes. I only watch mine because it's a good way to tell if anything is going bad. Like everyone said TUNE up everything. Clean dirty parts etc. Sometimes on older vehicles the fuel injectors spray pattern gets worse and mileage will suffer.