Quote:
Originally Posted by Jetboy
If a dealer did the diffs and transfer case - it's all but guaranteed they used non-synthetic fluids to refill. Toyota uses synthetic gear lubes in all the cases. So you're going to lose some mpg from that, but probably not a lot. Maybe 1mpg.
Do you have an lift, level kit, or aftermarket roof rack? Or even a bug deflector? All of those will hurt your highway mileage. GM did a pretty good study a while back that showed that a bug deflector alone will cost about 1mpg.
The common issue on the 5vz (your 3rd gen 4R) was the O2 sensors. They could essentially wear out, but you wouldn't know because the engine wouldn't identify them as having an issue. So over time they'd slowly cause a slight rich burn condition and fuel mileage would drop. I considered it sort of like preventative maintenance on my 1996. I changed them at 150 and 200k miles. Both times I had a noticeable bump up in fuel economy after.
Those are the big ones I can think of. I don't think I'm aware of any O2 sensor issues on the 5th gens though.
The wheel bearings usually start making a lot of nose is how you know they're bad. Not from anything mpg related. If they were causing excessive drag, they'd overheat and fail pretty fast. They don't have a lot of cooling ability and the thermal runaway happens pretty quick if something goes wrong that increases friction a lot.
The one thing that can cause excess drag and you may not notice is a seized brake caliper or parking brake. After you drive next time put your hand on the wheels. The brakes will probably be kinda hot, so don't burn yourself, but feel if you can for any one of the wheels being a lot hotter than the others. That would suggest a frozen brake caliper.
Could also be your driving - style or the nature of your driving. Lots of city driving of course is going to reduce mpg. Driving north of about 90mph really kills the mpg too. The next time you're on an open stretch of highway on flat ground, reset the mpg calculator and see what it gets at 65mph. For a stock 4Runner you should get around 21mpg.
Finally - double check that your tires are inflated properly.
Those are all the ideas I know of.
Good luck.
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2014 SR5 with 349K miles. Running Cooper AT3 LT (e-rated) in stock size. Everything else is stock. MPG has declined from 19.1 last just to just over 16 currently as measured by fuel purchased and miles on a recent 1281 mile trip from Fullerton, CA to Stevensville, Montana running typically at 80 mph.
Back in December I was doing work that had the battery disconnected for about an hour and reset the ECM. It then started to experience low idle and intermittent stalling when coming to stop after warming up. I cleaned the MAF to no effect. I cleaned the throttle body which cured the low idle and stalling, but the best mpg we saw on the dash was 16.7 after recycling the ECM. Now we see 15.7 and the calculated mileage of 16 mpg.
Spark plugs are nearing 100K miles, so I have a new set of Denso Iridium Long Life on order. All fluids are synthetic. Rear brake pads recently replaced and front pads have 75% wear left. Recently cleaned and greased pins in front calipers along with greasing the shims and back of pads to eliminate a squeal when backing up on cold mornings. Air filter has about 10K miles on it and is relatively clean.
16 mpg is not going to make or break us, but I would like to recover to 19 mpg.
