gear oil

[BB92]

will synthetic gear oil in the rear diff help it run a few degrees cooler?

 

[BB92]

Bump

 

[adsm08]

Meh, not really. The extra cost of the full synthetic gear lube over the regular stuff, which is already expensive enough, is not worth it for the minimal "performance" gains one might see from it,

 

[4x4junkie]

I don't see why it wouldn't lower the temp a few degrees... After all it is more slippery. People have reported minor MPG gains with it which can only come from reduced friction.

FWIW, many of these trucks came factory with synthetic lube in the rearend (not sure 100% when Ford started doing it, but it would make sense that it was when they started claiming a 100,000 mile fluid change interval for the rear, which a '93 had).

 

[adsm08]

I don't see why it wouldn't lower the temp a few degrees... After all it is more slippery. People have reported minor MPG gains with it which can only come from reduced friction.

Yeah, but the regular stuff is $20 a quart, I can't imagine what the synthetic stuff costs. I just can't see the minor MPG gains being worth it, and since diffs aren't prone to overheating without being seriously low on fluid or having some other condition present with the bearings I don't see that lowering the temp any is going to help anything.

 

[4x4junkie]

Where the heck you buy your oil at? It's like $12-15 a gallon for dino oil here in So-Cal...

I seem to recall Royal Purple being about the price you mention, though that might've been some years ago.

Edit:
Autozone by me has Mobil-1 for $10.99/qt.
http://www.autozone.com/autozone/ac...75W-90-1-qt/_/N-25t1?itemIdentifier=1437_0_0_

And RP is $20.99
http://www.autozone.com/autozone/ac...W-90-1-qt/_/N-25t1?itemIdentifier=854795_0_0_

 

[adsm08]

Where the heck you buy your oil at?

At work. My price on a quart of Motorcraft semi 75-140 is $18 and change. Customer's price is $21.something.

 

[kimcrwbr1]

I agree with adsm08 if it is getting too hot you have other issues to iron out.