i have a 1991 runner with a 3.0. i just put on 32 inch bfg mtr's and im getting 10mpg on average . is there anyway to get better gas mileage without changing tires? i already have a kand n intake and a custom exhaust.

 

Whens the last time you did the O2 sensors? Also what gearing is in the truck, 4.10 will net that kinda mileage with the 3.0 slow.

 

i dont know when the o2 sensor was done last. the gearing is all stock.

 

Then you probably have 4.10, or 4.30 at best. Your 3.0 isnt the best in the mpg dept and now pushing those tires is killing it. Need taller gears.....and a new 02 sensor probably.

 

Yes, i would look at the O2 sensor for sure.

Also, when was the last time you did a general tune up?

 

so even if the o2 sensor is no good it won't throw a CEL until it's really bad?

 

I just went thru the same thing and as soon as i changed my 02 sensor it came back to about 15.3 mpg with 32x11.5 with 4:10s getting my 5.29s today hope to bring it up even more but regearing is definitly some thing to think about if your gonna stay at that tire size forever i was told 4:88s is the way to go i will be going 35s with 5:29s and hope to get better then 15.3

 

If you have an auto your gearing would be either 4.56 or 4.88's. If you went from the stock 225's to 32's then regearing would deffinitely help but if you went from the 31's then either O2 or complete tuneup is in order.

 

it was tuned the day before i bought it. i went to the 32's from 31's, but even with the 31's the mpg was horable. it is basically a brand new engine, it has less then 8k miles on it.

 

Wouldn't that indicate the problem is not based around your tire size?

 

Is your speedometer/odometer properly calibrated for the diameter of the larger than stock tires? Accurate measurement would be the first step.

 

my speedo is 2 or 3 mph off

 

It is deffinitely not your tires. Since it was just tuned-up then it could be your O2.

 

I second the O2's I'm running 4.88's with 33x12.5's and before the O2 bit it I was getting 15.5, now about 12mpg. I also recalibrated the speedo (was off by 10mph) that'll make it look like your not getting as good a mileage as you are.

 

ok ill check out the o2 senser, now where is the cheapest place to get one?

 

is it an auto or a manual? if an auto, you should expect a little bit worse mileage than a manual, but it shouldn't be near that bad. I've got a 3.0, 5spd, pushing 35x12.5 BFG MT's, regeared to 5.29's (look at the dark red curve). Not too bad IMO.

 

ever cleaned that k&n? I second the tune-up idea. Check your tire pressure as well. Also, if it doesn't already have manual hubs, those are definitely a nice thing to have. According to my haynes manual, it can also be timing-related. I run 32x11.5"s on my 3.0 with an automatic, stock gears, manual hubs. But mine probably weighs less as its a truck and not a 4runner.

 

its an auto, i have auto hubs. ive never cleaned the knN, when it was last tuned i had the timing advanced a bit for more power but it was nothing huge.
the tires are at 36psi