Diff oil of choice

Gnarvan · 03-16-2012, 11:38 AM

This topic may have been covered in the past but a quick lazy search couldn't find it so here goes.

Synthetic or regular oil in the differential? I need to change the oil in the diffs after the 500 mile break in period and am wondering what kind of oil to use. This question is probably as subjective as the "what's your favorite color" question but feel free to toss me your opinion.

I've been told Royal Purple is a top choice for the hot rodder crowd. A gearhead buddy of mine says he wouldn't put anything but synthetic in his diffs. The guy at the shop is old school and says to stick with regualr dyno oil.

Anyone on this forum have an opinion?

Ford_6L_E350 · 03-16-2012, 12:56 PM

Synthetic would be my choice also.

Mike

**daveb** · 03-16-2012, 01:01 PM

Amsoil synthetic here

SheepShagger · 03-16-2012, 09:53 PM

Royal Purple.
Don't forget that some diff oils will need the friction modifier additive.

Gnarvan · 03-17-2012, 05:50 AM

Quote:

Originally Posted by SheepShagger

Royal Purple.
Don't forget that some diff oils will need the friction modifier additive.

Where do you get the Royal Purple? Is it available at regular car parts stores?

The Detroit Truetracs I had installed aren't a clutch driven LSD. They are all gear driven and don't require any special type of oil.

JoeH · 03-17-2012, 08:24 AM

Are synthetics in differentials really needed? It's not an engine, rather just a bunch of gears with teeth. Normal gear oil is pretty tough stuff. That said, Amsoil sythetic extreme 75W-140 in mine.

The main advantage I can think of is a longer service interval but I sort of want to stick my nose in there every 20,000 miles anyway and see how the oil looks.

**BroncoHauler** · 03-17-2012, 08:51 AM

I've always used synthetics in my diffs in any vehicle that tows. Diffs can get very hot, and I prefer the extra margin afforded by synthetic oil.

Herb

SheepShagger · 03-17-2012, 10:26 AM

Quote:

Originally Posted by Gnarvan

Quote:

Originally Posted by SheepShagger

Royal Purple.
Don't forget that some diff oils will need the friction modifier additive.

Where do you get the Royal Purple? Is it available at regular car parts stores?

The Detroit Truetracs I had installed aren't a clutch driven LSD. They are all gear driven and don't require any special type of oil.

Yup, NAPA & O'Reilly stock it. But if you plan ahead online order might be cheaper since you'll need quite a few bottles.

carringb · 03-18-2012, 11:40 AM

Even Ford says the rear end should have synthetic.

I run 75w-140 because of the heavy weights I haul (up to 25,000 combined). Otherwise, I would probably run 75w-90 since that will improve fuel economy ever so slightly.

cellularSTEVE · 03-18-2012, 01:16 PM

I use Synthetic from Torco.

steve