Major Decrease in MPG

I have an 07 prerunner with 53000 miles on it, but about 2 months ago the gas mileage went from 16-18 mpg in the city to about 10-12 mpg.. anyone know why this could be or any solutions?

 

Wintertime gas blend.

 

Also are you up with maint. and have you checked your tire pressure recenlty?

 

Could be a combination of things. Winter gas blend, winter driving, tire pressure.

You're almost ready for your second spark plug replacement. I suppose they could be worn.

When was the air filter last checked or changed?

Have your driving habits changed? Even a 5 mph increase in highway speed can cause a big drop in MPG.

 

I got my last maintenance at 50k, and tire pressure is good. And yeah I had no idea winter time could affect gas mileage so drastically. I know the big 60k mile maintenance is coming up, maybe some things need to be dealt with earlier than that? Also, I have been driving at 70 mph for a 40 mile commute twice a week... I reckon stuff just adds up, I just didnt know if 10-12 mpg is normal at all. Are there ways to avoid winter blend for next year?

 

Or what exactly is winter gas blend, haha sorry. i like to learn stuff

 

they put additives to prevent frost and ice build up in fuel systems which kills mpg's.

 

I am down about 2 mpg also.

 

Not a bit of it. You lose more than .3-.7 mpg on "winter gas" you've got a serious engine problem. Or at least engine control problem.


Hanging brakes, bad wheel bearings, clogged injectors... much more than that and you should be saying "and its running rough or weak".

Are you in 4x4 the whole time? That'll bring it down some.

You're right in the bottom end of wheel bearing failure mileage. Ice can hang the parking brake (didn't catch your area, and can't see while typing).

Get an IR thermometer (little pistol grip thing with a laser pointer) and shoot each wheel/hub. They should all be about the same after driving. If one's 1300 degrees, you've got a problem. If it is a hanging brake, I'd say its a rear, or you'd be complaining about it driving off the road.

 

Its a price vs pollution vs regulations thing. Does not reduce energy nearly like a lot of the wikken folk around here believe it does.

http://www.theoildrum.com/story/2006/9/13/234043/431

10-12 mpg is hard to get in a 6 speed 4x4 worst I've gotten is 16 while hammering it around during a death metal relapse. Without a mechanical problem, you got to drive like an small dicked teen to get that. Or have massive tires and injectors. Which is like the same thing. To be terribly assy.

 

bad O2?
bad water temp sensor?
send a signal to the ecu that the engine is always cold and it uses more fuel?

(you guys do know an O2 Sensor has to breathe (or suck in air) where the wire harness meets the metal of the O2, so a dirty or covered with mud O2 sensor will give a bad reading)

I am just guessing whats wrong, but its easy to take a quick look at ur O2 sensors and make sure they are clean.

 

What about cleaning the Maf sensor? I cleaned the one in my 98 4runner and it helped alot with gas mileage...

 

I agree! The mass air flow sensor will give bad mpg,, inspecting and cleaning it doesn't hurt.
(all of these sensors tell the ecu to adjust the fuel (injectors stay open longer)

 

I'm definitely thinking its something to do with the injectors.. when i was going only 230 miles on a full tank, my friend told me to try to put some "lucas" stuff that goes into the gas tank and is suppose to somewhat clean the fuel injectors. And it helped my mpg to go up to about 13 or 14. I'm due to get that whole fuel system and injectors cleaned at 60k miles i believe. And for running rougher or weaker during this downturn in mpg's.. You could say i could tell a slight difference from before, but not too much of a difference. Just enough to where it was slightly noticeable. I'm just debating on skipping my 55k mile maintenance and just getting the big 60k mile one done early and hopefully that'll help? or maybe at least to give the dealership a chance to assess to the problem.

 

Ethanol???

 

And this may be important to fit into the equation that i forgot about.. I read about another guy getting about the same amount of mpg as me on here, and him and i are running 265/75/16 tires and doing in city driving.

 

ya don't lose 4-10 mpg on 10% ethanol.

Other than the maf sensor being damaged slightly.. I would think any of those other things would throw codes. Maybe they wouldn't turn on the CEL if they didn't cause too much pollution and wouldn't blink it unless they were going to blow up the engine.
Pull your codes and see... You shouldn't have any..

 

On top of the Winter blend that I've found does cut mpg, there is of course longer warm up times for engine, oil, and tires. But in many places, including counties around the major urban areas of PA (Phl, Pitt, Scranton W-B) there is a mandated change to an oxygenated fuel (October to May) that is even less efficient. Couple that with it being yet another excuse for fuel distributors to tack a couple cents/gallon onto their pump prices and it makes a serious dent in your mp$. The combination generally results in about 10% worse fuel mpg and a couple percent more expensive. My fuel cost per mile is about 13% worse in winter. It is a little hard to make this comparison since the price of gas is pretty fluid for more reasons than I can keep track of.

 

I'm down about 1-2 mpg right now...