I have been getting bad gas mileage for a while now in my 3rd gen 4runner. im getting right around 13 mpg. i was talking to another guy who has the same set up as me but has 4.56s in the rear and he also has 33" mud terrains, i have 32" muds, and he is getting around 19 mpg. i was wondering if my before cat o2 sensor, MAF, or even possibly a dirty/clogged cat could be effecting it that bad?

 

i am going to try seafoam, i heard that stuff works wonders. but if it doesnt make to much of a difference i will go from there i guess

 

this is probably unrelated, my 96 tacoma appearred to be getting poor milage(i guess that would be kilometerage where i come from)but the fuel gauge registered empty about 160 km (100 miles) to soon. just for the heck of it, full jerry can in tow, i kept driving past empty. wouldn`t ya know it, gauge went back up to normal then back down at the right count on the trip counter. something to look at. i too had checked all the things you have.

 

I was having the same problem with my Tacoma. Last time I filled up I had done about 12 mpg! I have an almost stock setup and I know a guy who is bragging about his 22mpg with bone a bone stock truck. same drive train... only difference is I have a cold air intake on mine.

 

did you end up fixing your tacoma's gas mileage?

 

I am currently noticing the same thing on my 3rd Gen 4 runner. I calculate my mpg just about every time I fill the tank I was averaging around 19 mpg and am suddenly getting around 13 mpg on the last 3 tanks. I drove 11 miles this morning and watched my gas gauge do a dramatic drop. No modifications have been made for at least 3 months and I was definitely averaging 19 after any changes were made. Did you figure out what was causing your bad mpg. Upstream (front) O2 sensor? MAP? MAF? I hate to start changing things out if I don't need to as it can get pretty expensive. Any help would be appreciated...

 

welcome to the club guys! lol... I have 295/75/16 with stock 4.30 gears. I have replaced the pre-cat 02 sensor, new fuel filter, cleaned the tb/maf/air filter. I also have the ISR mod and deck plate mod. I get a whooping 13mpg average. My GPS shows that when I am going 65, actual speed is 68.

 

I get about 14mpg with my truck... 3.90s and 33" muds. However, I drive up a pretty good hill every day, and that really sucks down my mileage. Mileage goes up to about 16mpg if I avoid that hill.

 

Same boat. Thought full maintenance would cure things but mileage still sucks. Taking into consideration my upsizing in tires as well as my test on the freeway to determine true speed, I'm getting about 15 - 16 mpg. The only thing I haven't done was swap out my 02 sensor, which someone here did w/o a CEL and no change in mpg. I don't have a CEL so I'm not swapping mine out.

I do mostly street driving and go up a steep hill daily so this could be a couple of factors on the mpg. If I do a lot of highway driving on a tank of gas, I may get 1 - 2 mpg more but that's driving over 70 mph. I think people that claim 19 and above mpg just granny the gas pedal. That's the only way I can see them getting this kind of mpg.

 

I think the hill factor sucks a crapload of gas as I go up and down two fairly steep hills twice a day.

 

My CEL light has not come on either. However, what worries me is that this is a very new problem. I've made no recent mods and my driving style has not changed. I have been driving the same 11 mile, no stop and go, 55mph route to for the last month and have noticed this change within that time period. This morning, on my 11 mile adventure, I watched the gas gauge drop from 3/4 -2/3 of a tank or more to 1/2 a tank. Seems to be getting worse, however, I won't know until I fill up again. A buddy of mine is attributing it to the weather, because it has been getting so cold at night, but I don't think that would cause a 5-6mpg change. It is damn cold though!!!

 

Although this issue has been beat to death, let me mention some obvious things:

1. Winter fuel supplies are typically formulated to reduce emisions at the mercy of fuel economy.

2. tire pressure typically drops 1 PSI per 10 degree F. drop in temperature, so if you last checked tire pressure at 70 deg. F and now it's 10 deg. F., you're running your tires 6 PSI lower which will significantly reduce fuel economy.

3. Winter driving this time of year includes holiday traffic, "shopping" driving (vs. my normal backroad driving) and more warm-up time, all of which affect economy.


I typically roll-off about 2-3 mpg from December thru February or March here in PA. I average 20 MPG most of the year. Although last nites fill-up calculated out to about 15 MPG, I don't panic until I've seen 3 or more consecutive "brow-raising" data points.

 

Rick F makes some good points. Have you checked your tire pressure? I checked mine recently and the rears, although even, were much lower than the fronts. Also, is your tank dropping and are your fillups still the same amount? Our 3rd gens have had issues with tank readings so I'm trying to understand if you're still filling up with the same amount of gas. Your CEL may come up pretty soon if you're noticing that much mpg dropoff. Also, our O2 sensors tend to get lazy as they get older so they're not as efficient.

 

Rick F. Makes some great points. Good to see some numbers to back it up. I do know I am running my tires a little lower than I probobly should be as I was doing some backcountry not too long ago. I'm doing some general maintenance this evening so I will definitly make the air pressure adjustments as well as a few other things I'll be checking out. Their's no holiday traffic or shopping driving in my part of the country so that would not account for it. I have however taken into account morning warm-up and have tried to cut this to as little as possible to see if it makes a difference. We'll see on my next fill up.