Daddyota

Hello faithful yotatechers,

My 86 22re 4Runner has a v6 radiator the previous owner installed. The engine doesn't get very hot according to temp gauge (it works) and the needle goes up a third of the way when warmed up. My question is, will a larger radiator cause worse fuel efficiency because it is keeping the engine cooler? My fuel economy sucks at around 14-15 no matter how I drive and my truck is stock except it's rolling on 32s, has a bumper and winch. I did a search and found no info. Any thoughts?

tj884Rdlx

The rad does not control how hot the engine runs. The thermostat does.

You can modify what temp your engine runs by changing the thermostat to a different temp rating. If you want it warmer, go up 10 degrees. But i doubt that's your problem.

Your mileage at 14-15 is typical of a truck on 32s with stock gearing. Have you regeared to 4.56 or 4.88??

To restore factory mpg, either regear or go back to 235/75s to restore the factory rpms-to-mph ratio.

Fyi i get 13-14 on 33s with 4.88s but i run 70 mph frequently, which vacuums gas trying to keep this brick at hwy speeds. 14-15 is good on 32s.

Also, clean your air filter and inflate tires as specified. Just in case.

Daddyota

I have stock 4.56 gearing. Air filter is good and tire pressure is good. I just thought I would be getting better highway FE when I drive careful.

tj884Rdlx

Is it automatic? 4.56 gears were factory on automatics to make up for the lack of a few gears in the tranny. They still were paired to 235s or max 31s with the towing package. You'd benefit with smaller tires which put you back into the most efficient RPM range as you drive.

If you are constantly driving no faster than like 45mph I'd expect a little better, but pretty much I'm getting 13-14 myself, so you're not really out of the average.

These things are fuel efficient compared to old American cars. But not to later cars so much. You can also modify timing to affect mpg but nothing affects it more than driving nice and slow from stops and staying under 55. Good luck!

Daddyota

Son of a gun! I have a 5 speed. All I know is that the gearing is stock. So the thermostat controls the cooling/heating? So bigger radiators dont equal cooler engines?

tj884Rdlx

No, bigger rad = more capacity = faster cooling. But where it cools down to, is controlled by t-stat rating. When that stat closes, rad is cut out of the loop until it opens again.

I don't know the temp for v6 but on my 22re many like me change the stat to one with a bypass valve, so it stays mostly closed a little longer and allows warmer operating temp. I think it's a 180. There's much historical discussion on doing this for my engine so maybe yours too.

Edit: Duh you said you had 22re. Yeah, read about tstats. Buy a quality one from Toyota using the suggested part number in the tstat threads. You may want to change that out anyway. But it's not affecting your mileage.

If you are not certain you can calculate your true gear ratio by lifting the rear and hand turning a wheel while counting the drive shaft turns. Then you'll know. If you are really running 4.10s with 32s that would totally justify your lower MPGs.

arlindsay1992

iTrader: (8)

For what it's worth, if you have larger tires your odometer will be off the same amount as your speedometer. You need to multiply your mileage by the ratio between new tire size and original tire size. I run 33's, original tires are 29's. 33/29 is 1.137. With stock 4.10's, W56, and a 22RE my 87 4Runner gets 20 MPG on the highway.


To correctly calculate mileage:


Miles / Gallons X 1.137 (or whatever your ratio is)


Many people forget to do the last step and believe their mileage drops with bigger tires when in reality it's not as big of a difference. The truck is moving farther for each rotation of the engine so it counteracts the extra weight.

arlindsay1992

iTrader: (8)

You can also get a speedometer cable gear with a different amount of teeth like I did so that your speedometer and odometer are both correct.

Daddyota

Thanks for the tip Arlind! That helps. I never considered that.

Outsane

rock sliders, tube winch bumper and rear rock bumper.

are also not helping with the Gas mileage...