Change tires for better gas mileage

[Richard Evans]

Hey guys, never posted before, but enjoy all your rides. I have a '92 4x4 Ranger with the 4.0L engine. I bought the truck a year ago, replaced the radiator with a new 3 core, installed an electric fan, changed all the fluids, and have done a bit of wheelin in the mountains of Nevada. It has 31 x 10.50 - 15 tires right now. No lift. I get 17 miles to the gallon if I drive 65 on the interstate. I drive about 100 miles a day round trip.

So the question is, these tires are gettin worn down, and was wondering what you guys thought about 235/75-15 tires. I know they are quite a bit smaller and narrower and should improve gas mileage. How much improvement can I see do you think? Anyone ever done this? Is it worth it with higher gas prices. I don't think for the wheeling I do, that the smaller tire will be an issue.

 

[4x4junkie]

Do you know what axle gear ratio your truck has? (this will make a huge difference in how much there is to gain from the smaller tires)

 

[Original_Ranger84]

Well a 235 is about 2 inchs shorter and an inch narrower, but first I would try sticking to 55 on the highway... I found in my 3.0L if I stick to the speed limits I get 20 or 21 hwy goign between 60 and 70 but if I go down to 55 i can pull off 25 mpg.

Also tune up would probably net a few mpg's if it was in major need of one. Personally though with larger tires you would be getting better mpg's on the highway, because it take very little power to keep a car moving rather then getting it moving. And with a larger tire each rotation carries the car further.

 

[lneidlinger]

My ranger was a ranger "s" fleet vehicle, meaning it was a barebones no frills (i.e lightest) truck but Portage Parks decided it needed a 4.0 and the A4LD.

When I bought it, it had P195/70R14's on it, a bit undersized to what it came with from the factory. All 2wd's have 3.08 gears. Even so it got about 24-25mpg driving on the long, straight back roads cruising around 55 (it also would do burnouts with hardly any throttle which was actually quite annoying). When I changed to P225/75R15's the mileage is worse if cruising around town but I find driving on the back roads it gets about 27mpg now, but I have to be going about 55 to get it to go into overdrive versus about 50 before.

 

[doorgunner]

Going slightly shorter....31" to 30" will help gas mileage...it causes a rise in vacuum.....a tire that is too tall drops the engine vacuum/gas mileage, even though the tire moves the vehicle farther per revolution--been there made that mistake)....getting the engine to run about 2200 rpm with the right size tires will help....

I installed 2.94 ring&pinion in my street-Ranger....when it goes into overdrive the vacuum gauge went from 20hg down to 15 hg/gas mileage did the same--grrrrrrr....my next set of tires will be an inch less on the diameter to get the vacuum back up to 20 hg.....

 

[Richard Evans]

Not sure what the gears are in the rear end, but being it is 4x4, i would have to change both front and rear gears. I think it owuld take a long time to see any payback in gas savings for the cost of the gear changes.
The stock tire for this truck is 215/70-15, which I think is too small. That is a 27.7" diameter tire.

What kind of mileage are guys getting out of a stock 4x4 ranger with factory tires? Anyone know?

 

[JohnnyO]

Less mass and rolling resistance = better mpg.

 

[doorgunner]

Not sure what the gears are in the rear end, but being it is 4x4, i would have to change both front and rear gears. I think it owuld take a long time to see any payback in gas savings for the cost of the gear changes.
The stock tire for this truck is 215/70-15, which I think is too small. That is a 27.7" diameter tire.

What kind of mileage are guys getting out of a stock 4x4 ranger with factory tires? Anyone know?

no......i'd never expect you to change 4 x 4 gears to get better gas mileage....changing tire diameter would be the way to go, but I would keep as much width as possible...besides....new tires when needed are about the most inexpensive way to get positive results....

 

[RustedRanger]

+1 doorgunner I been there done that also. Bigger tires will help mpg's on some vehicles that have big engines with lot's of low end torque. My 87 had 235/70/15's on it when I got it and I saw an increase by going to 225/70/15's. Like doorgunner mentioned,around 2200 rpm cruise is about right for these motors. With the 225's mine is at about 2100 rpm at 55 mph and last I checked I was getting around 22 mpg.

 

[Daniel_187]

I have the same tire size as OP is wanting, but I have an 02 4x4 and have been getting around 17.76 MPGs and its really knida of torquey

 

[kemo]

odd... shows that stock tire size for your truck is 215/75-15 on every tire site i've been to.

I'd get firestone destination a/t's for that thing.

 

[4x4junkie]

Not sure what the gears are in the rear end, but being it is 4x4, i would have to change both front and rear gears. I think it owuld take a long time to see any payback in gas savings for the cost of the gear changes.
The stock tire for this truck is 215/70-15, which I think is too small. That is a 27.7" diameter tire.

What kind of mileage are guys getting out of a stock 4x4 ranger with factory tires? Anyone know?

215/70R15 is what I was gonna suggest if you have 3.27 gears. If you have 3.73s, then I wouldn't expect to gain a whole lot with smaller tires.

As Original said, slowing down a bit (55-60 MPH) will easily get you another 1-2 MPG. You might also try inflating your tires to the max pressure listed on the sidewall, which will reduce their rolling resistance. Only thing with that though is you'll need to rotate them diligently to keep the rears from wearing their centers out.

FWIW, I get about 21 with my '94 doing 60 MPH (4.0L stickshift, 4.10 gears, 33x12.50s). I seem to recall about 23-24 MPG when it was stock, but that was a long time ago.

 

[racsan]

mine is a '93 supercab with stock 235-15's manual trans, 4x4,3.73 gearing. i get 19.5 at the very best, most of the time my combined average is 17-18. optional tire size for mine factory was 265-15's which is darn close to a 31-10.50-15. tread design factors in to fuel milage also, if you dont need a off-highway tire, go with normal street radials or a all-terrain tire. mud tires look cool, but wear fast and tend to use more gas. i also have a vaccum guage and try to maintain the highest reading possible. theres times that using 4rth gear gives me a higher more steady reading than 5th gear. its a little hard to know for certian how much your milage improves when you change tires because then your speedometer/odometer is off. my winter tires used to be 215-75-15's, i could tell i had more low end, but really couldnt get a accurate fuel milage reading, and since more fuel is used during the winter (for multiple reasons i wont go into unless you want me to) i rarely ever check winter milage (its 15 at best). dont forget the little things like tire pressure being correct and the air filter in good condition. find out your gear ratio. if you have a tach and your turning about 2,000 in 5th gear at 55 mph, thats what my 3.73's do. 1,600 would be about what you would expect in o/d @ 55 with 3.55's doubt you would have 4.10's, i suspect you would be around 2,300 in o/d @ 55 with them but im just guessing there.

 

[Original_Ranger84]

I don't know I went from 225's on my truck and getting 19 hwy to getting almost 25 hwy consistantly when I switched to 31's

 

[strvger]

mine did better with tall, skinny tires over the original 195/75x15.
you could get some like mine, 215/85x16, about 31 inches tall, E rated (10 ply equiv.) and air them up to maybe 80 psi. those rock hard tires would allow less rolling resistance and drag, thus getting more mpg's... in theory. however, at that psi, you're going to be airborne with every little bump or pot hole, thus loosing necessary ground contact and loosing a little in the mpg department.
guess it's a wash.
i'll keep what i have and keep them aired to about 28psi and be happy.