poor fuel milage

[tyr0981]

so first i'd like to thank everyone on this forum, so far all you guys /gals have helped me figure out all my future plans with my 4runner! ARB Bumper winch, and tires, interior lighting questions, i'm sure their's more!

so ever since i increased my tire size from the OEM (whatever they where) to the current 265/75R16's, my fuel "economy" took a nose dive, went from 25MPG on the freeway to~17ish highway and ~18 in the city to around 12ish. I realize i've changed the gear ratio with the bigger tires, but i'm kinda vague on how to figure out what i need to change the ratio to, to restore it to factory settings, or its best performance...? and if i should also do a locking Dif / limited slip while i've got the differential opened up as-well....

so if you've got some answers and or experience, i'd love to hear your story on how i can regain some of my lost fuel economy! i'm only making about ~200 miles per tank (when i drive nice and easy), i know she can do better! thanks gentlemen!

 

[mien4x4]

dam man that sounds bad because im getting 200 miles per tank with 35s with stock gears maybe you need a full tune up?

 

[PitbullRescuer]

25 Highway, 18 City??? You sure about that? Those are some of the highest numbers I've ever heard for a 3rd gen. 265/75 are only one size up from stock, the difference in fuel economy should be almost nothing.

That said, we need more info on your truck. Which engine? Manual or Auto trans? How many miles? 4WD or 2WD? What maintenance has been done, etc?

 

[Kung]

^^^ What he said. I have 265/70R16's with the stock gears; and about the best I've ever gotten is 20 or so (which is pretty darn good for the stock). If you had 25MPG I wanna know how. LOL

 

[tyr0981]

Well it's been awhile since I saw 25mpg, and that was all freeways except off ramps for fuel and food. So 2k 4runner 5vzfe 240k on the speedo, automatic, engine is around 160k miles (transplant), I've tried all maintenance that came to mind, seafoam the fuel, changed fuel filter, air filter is a K&N, new plugs, wires, coils, regular oil changes, I think the only part I haven't tinkered with is the exhaust...

Edit: and yes 4wd.

 

[tyr0981]

nobody has additional ideas eh... well i did used to do pretty well on the freeways but now it's pretty much all terrible....

no supercharger either....

:violin:

 

[BTO]

so ever since i increased my tire size from the OEM (whatever they where) to the current 265/75R16's, my fuel "economy" took a nose dive, went from 25MPG on the freeway to~17ish highway and ~18 in the city to around 12ish. I realize i've changed the gear ratio with the bigger tires, but i'm kinda vague on how to figure out what i need to change the ratio to, to restore it to factory settings, or its best performance...? and if i should also do a locking Dif / limited slip while i've got the differential opened up as-well....

I think the stock is 265/70/16 so you only increased the size a tiny bit. Certainly not a big enough jump to warrant a regear. Maybe you lost most of the MPG because you went to high rolling resistance ATs and heavy mass like load range D. Maybe you have other things going on like you lifted or added a heavy bumper?

 

[tyr0981]

well that's an interesting point, i did put on more aggressive A/T terrain tires, not like mud terrain's though, they are D rated tires... come to think of it, i think it was around the same time i put the 2.5" old man EMU lift, that their was a big drop in fuel economy maybe i'm fighting the wind a little more....?

but in town driving dropped off too, i suppose it could be a combo of the issues with tires and lift....?

i was hoping their was some mysterious issue i wasn't aware of and could just replace/ upgrade something.....

:moping:

 

[02SE]

well that's an interesting point, i did put on more aggressive A/T terrain tires, not like mud terrain's though, they are D rated tires... come to think of it, i think it was around the same time i put the 2.5" old man EMU lift, that their was a big drop in fuel economy maybe i'm fighting the wind a little more....?

but in town driving dropped off too, i suppose it could be a combo of the issues with tires and lift....?

i was hoping their was some mysterious issue i wasn't aware of and could just replace/ upgrade something.....

:moping:

Going from a stock size light P-rated tire, to a larger, heavier load range D LT tire, and in a more aggressive A/T tread pattern, could easily account for a couple MPG. The lift will further hurt the already poor aerodynamic drag coefficient of these trucks. Which could mean an additional couple MPG drop, depending on how fast you drive.

On the highway, 55-60 mph is about the sweet spot for good MPG in my 4Runner. Of course you're also likely to get run off the road if driving those relatively slow speeds on most highways. I can watch my MPG drop on my Ultragauge, the faster I go.

 

[TRDteen]

I'm getting this same problem. I get around 160 - 175 miles per tank averaging 12.4 MPG. I'm going to try cleaning the throttle body, and do a sea foam. If that works I will let you know!

 

[tyr0981]

yeah i cleaned the throttle body and IAS valve, idles smoother now (because the IAS was plugged up with crap from the EGR) but no change in fuel economy for me.....


:whipping2

 

[runnaz]

My 99 went from about 16-17 city/highway to 12 last year and I don't have a clue why. I've had the same size/type tires on it for the past 8 years so I know that isn't why. I've replaced plugs, wires, fuel filter. I've cleaned the MAF and throttle body, and put seafoam in the gas tank. Still no improvement.

 

[Kung]

Here's an idea (may be a dumb one): Specifically when did you get your new tires and the like?

I'm curious as to whether or not you just happened to buy them around the same time that gas stations tend to switch to their 'winter' blend, which, I've noticed, usually gets you worse MPG.

 

[nissanh]

The best I had was 21.5 at 72 MPH. Usually it is 20 to 21 MPG. All highway. This is in Westcoast CA and NV

Ever since I moved into LA, TX area, it is doing 16-17 MPG on highway. Never got 20 MPG. IS this something to do with the quality of the fuel? Car is same. Nothing changed.

I did a mass air flow sensor cleanup today. Now the truck starts up very easily... like in a second.... Hopefully this will improve the mileage.

 

[tyr0981]

i've been through multiple bouts of having to clean the little wires in the MAF, it's something that i've "eyeballed" as a potential cause, but once i clean the K&N oil off of it after a filter clean, it's happy again until i clean the filter again...

The changed in MPG happened... 5 year or so ago, pretty much after i put the OME lift on and the taller tires, i think those would NOT improve my mileage, but to loose an average of 5 MPG across the board seamed a little high to me....