22RE manual trans,my mileage has gone down to 20 mpgs from around 25.What should I check/service to improve this?

 

Trans fluid, diff fluid, engine oil level, change all filters, plugs, check 02 censor or change, tire pressure, alignment...

 

I'd be thrilled for 20mpg from a 4x4 if I were you. Your driving style and gas blends could make up that difference. Do you have gas logs to verify your average gas mileage has actually gone down or is this a guess?

 

If you're running winter gasoline blended with more ethanol, that will also cost you mileage. Ethanol has about 1/2 the energy/gallon as gasoline, so a blend of 15% ethanol will reduce mileage by about 7-8%.

 

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I clocked it at 25 and that was doing slightly more highway driving but not by a great degree. my auto used to get 20,but I think 25% reduction is quite a big difference.Sure it could be many factors,been 60k since last tune up. I am going to do a tune and check timing(compression while I got the plugs out) pcv and valve adjustment. Will report back any findings.

 

I would change out the O2 sensor first. That seems to be the biggest culprit for MPG drop when nothing else has changed. If it's never been replaced, I GUARANTEE you'll see an increase in MPG.

 

Winter gas, more idling, wind, more city driving, traffic, hauling more load, lower PSI in the tires (colder weather), all can have a drastic effect on gas mileage.
You're laughing if you get more than 20MPG.

 

25MPG? I don't think I've ever seen that from my '87 4Runner even when it was new. Even the original factory specs call out 20 city and 23 highway, but with the 30" tires I pretty much see just under 17MPG for a mix of city and highway.

Does anyone else feel that an oxygen sensor change is going to make a difference, especially considering it passes CA smog testing w/o issue?

 

I would be so very happy with 20mpg. I get 12 to 15 mpg

If your getting 25mpg it must be downhill out of gear.

Just how many times did you manage to get 25mpg ?/

Unless your using very controlled conditions the best you will get is a good guess.

Want the best mileage run high tire pressure so you have the least amount of rubber in contact with the road.

Strip all excess weight out of the vehicle( most days I have at least 500 extra pounds)

Good tune up Don`t forget the air filter

 

On highway I have always gotten 25 with my manual.My auto got 20.Stock tires.

 

Tune up with factory parts,air filter,pcv valve, valve clearance adjustment(exaust were .002 too tight,intakes were in spec),oil change,new rear diff oil,new man tran oil.With pretty lengthy warmups its back to 25.

 

A new Denso brand O2 sensor was may still help because these sensors still foul up over time. It still may be fine for smog but just far off enough to affect your mileage.

 

I get 25 as well. Manual with stock tires.