Fan clutch oil mod: mpg hit?

[e9999]

searched but didn't see any obvious thread (and couldn't bring myself to read through all 2 million posts in LT and Tools' threads - sorry, bear with me, pls... )


so, you did put in the higher weight oil in your clutch. No doubt that has resulted in the fan being on more than before. But have you seen any significant difference in mpg after doing that? I'm thinking the fan must gobble up a bunch of power. (And the oil in the engine may be colder so perhaps thicker, although that is likely a second order effect -if anything- with multigrade oil.)

No doubt it's a good thing -and for some, critical- that the engine runs cooler but curious as to the effect on fuel economy, if any... If it's gonna cost me 1mpg, say, to lower the temp from 195 to 185 I may not indulge...

What say you?

 

[Stevesnj]

I say it costs more to replace the head gasket, radiator and other cooling components than the cost of a mpg hit. I think the hit is negligible.

 

[jwilber]

Just did mine so no way to
judge on mpg but cools a ton better so x2 on cheaper than a head gasket. You don't have to go with the big number fluids. I went with 10k and its a big difference

 

[e9999]

I'm aware of the cooling and HG issues on the 80. Leaving that aside, I'm talking about the tech side of mpg effect.

I'm thinking that this can't be totally insignificant or Toyota might have had the fan run full blast all the time. (Although noise could also have been a factor, perhaps?) I would have thought this would have been discussed here given our gashogs travails, but can't remember seeing that addressed.

 

[Wheelingnoob]

I'm not in a hot climate but I did not notice any significant change with I went up to 10cst fluid. It does engage now though where as before it never would engage.

I would say it was less than .25 mpg, I have tracked all my tanks of fuel and it made no noticeable difference.

 

[LandCruiserPhil]

searched but didn't see any obvious thread (and couldn't bring myself to read through all 2 million posts in LT and Tools' threads - sorry, bear with me, pls... )


so, you did put in the higher weight oil in your clutch. No doubt that has resulted in the fan being on more than before. But have you seen any significant difference in mpg after doing that? I'm thinking the fan must gobble up a bunch of power. (And the oil in the engine may be colder so perhaps thicker, although that is likely a second order effect -if anything- with multigrade oil.)

No doubt it's a good thing -and for some, critical- that the engine runs cooler but curious as to the effect on fuel economy, if any... If it's gonna cost me 1mpg, say, to lower the temp from 195 to 185 I may not indulge...

What say you?

Dont count on lowering your temp to 185° that is below normal operating temps. Also too low for peak performance. I run a ToolRUs fan clutch set at 125° and get excellent results on cooling and MPG. See my thread How to get 15MPG with a ScanGauge My normal water temps summer/winter 188°-193°.

I cant speak for LT fan clutch performance but I do know his is set at 95°. You may want to check with LT depending on where you live . The way I understand the working of the fan clutch if set at 95° In AZ that would mean it would be opening before you started your LC most of the year, possible effecting your MPG if you live in a hot area of the country.

 

[SUMMIT CRUISERS]

I tried 20k cst in our 92. Drove it on a 100 degree day on the highway at speeds about 65 (that's about as fast as it wanted to go) Fan was roaring the whole time and what power the 3FE did produce was seriously affected. Changed to 15K and no roaring at highway speeds (more power, more MPG's). We just finished a 2,200 mile trip 3 weeks ago in 100+ temps pulling a loaded M416. Operating temps never went over the half way mark the whole trip. MPG's weren't great but we averaged about 12.4.

 

[jcope]

Interesting point.

Is it wise to do the modification if you're already operating in the normal range, particularly if you're going to cause the vehicle to run more inefficiently overall?

 

[BrotherRob]

I'm running 25k in a blue hub. I have not noticed a change in mileage. I'm sure if you put it on a dyno there would be a miniscule difference but not enough to fret over.

 

[SUMMIT CRUISERS]

Interesting point.

Is it wise to do the modification if you're already operating in the normal range, particularly if you're going to cause the vehicle to run more inefficiently overall?

Ours was heating up on our high altitude off-road trips. Changed radiator, installed GTP hood vents, 12" pusher fan, installed new blue hub clutch and still over-heating in Low range on very steep inclines. Upgraded the fluid to 15K and no problems for 2 years straight.

 

[landtank]

theoretically if two identical trucks in identical conditions were operating at the same engine temperature then the drag produced by the fan clutch would be the same. If not then they would be running at different temperatures.

If more drag increases cooling and costs MPG then you need to decide at what point do you sacrifice engine cooling to gain MPG.

For me engine cooling is quite a bit higher on the want list than MPG.

 

[BrotherRob]

Interesting point.

Is it wise to do the modification if you're already operating in the normal range, particularly if you're going to cause the vehicle to run more inefficiently overall?

If you are in a cool climate and it's working, maybe not. If you are still on the original clutch, the oil has likely broken down. If so, a refill would be prudent, but you may not need the supped up performance.

The US clutches were filled with light weight oil to leek out .0001 extra MPG. For those of us living in the desert, they just don't keep up in the summer. Hence the thick oil to turn them into wind turbines. Otherwise the AC pretty much dies at idle.

 

[AFinn]

I'm here in phoenix too, and my rig list about 1mpg when I put a new blue hub with 20k CST from tools. Since I have list a couple more to bigger tires and neglect. I have 315 tires, and have to put 19-20 gal in at a pretty consistant 230 miles, on an uncorrected Speedo with stock gears. Usually drive a smaller car.

I have not had an issue with cooling at all tho. Middle of summer, ac on high......

 

[AFinn]

I been contemplating trying an elec. Just to see if any difference. A project for cooler times tho. ( I can hear tools cursing me under his breath from here )

 

[cary]

I have noticed no change in mileage with the Landtank clutch and I check every tank. If your are concerned, I would do the 15k cst fluid and calibrate the clutch to 115f.

 

[BrotherRob]

I been contemplating trying an elec. Just to see if any difference. A project for cooler times tho. ( I can hear tools cursing me under his breath from here )

Had an electric, pre mod days. A modded clutch works much better.

 

[Michael Hanson]

7 older cruisers running in Dallas this summer,stop and go traffic, trailer pulling, air on and 100-108 temp. No modifications to any fans.. no over heating. It can be done. Mike

 

[93yotasr5]

Electric seems like itd fail in a wet situation. I only use electric fans on my street vehicles.
Running 70mph on the freeway with an old eaton clutch fan. And I got up to 201. Higher than I want it to be, so I'm going to put 15k in my spare and try it out and see if I can keep it at a high of 190

 

[Tools R Us]

...
so, you did put in the higher weight oil in your clutch. No doubt that has resulted in the fan being on more than before.

Nope, going to higher viscosity fluid only, will not cause it to be "on" more often. The thermo valve is still the same, so will come "on" and turn "off" at the same cooler output air temps. One could argue and my observation agrees, that it will actually be "on" for less time, especially time at the higher valve levels. This is because, the fan is more powerful, so it more quickly establishes a strong airflow, does the job and backs off to a lower valve opening level or "off".

If you tune the valve, can make it "on" more or less often, your preference. My observation is; Toyota got this one real close, at least for the desert climate that I have experience with. If tuned cooler, they run a lot when not needed, if tuned warmer, may save a tiny bit of fuel?

I check, but don't mess with most of the valves. The exception is the Eaton clutches, lots of them come "on" at ~135-150F, so tune them to ~125F. Not sure that even matters, they are original to the rig, so have been working, cooling the rig for many years/miles before the fluid went soft?

... I'm thinking the fan must gobble up a bunch of power. ...

Maybe, maybe not, it takes a given amount of power to cool the rig, pick how/where you going to get it. It's true that the clutch is capable of delivering higher torque levels. But the stock clutches, with old fluid or new, wimpy blue hubs, spend a lot of time "on" attempting to do the job. You will hear a tuned clutch, they can be somewhat rude, but it's more rare (mostly after a heat soak) and for shorter duration. If the valve is tuned too cool or it is overfilled with fluid, then it will be "on" more often than needed or all of the time.

 

[Tools R Us]

I been contemplating trying an elec. Just to see if any difference. A project for cooler times tho. ( I can hear tools cursing me under his breath from here )

Do what you want, report your findings. Have been spending time at the pick & pill, have seen lots of looking fans, including some hydraulic.

IMHO, the '80 is primary purpose is for wheeling. My experience says; the clutch fan has the most power potential, is dead simple, robust, killer reliable, etc, all great attributes for a wheeling setup, especially in the desert.