Ok,
Who has used royal purple in their differentials ?? Have you had good luck with it? And did you use the Ford limited slip additive with it???
Royal Purple says that you don`t need to add any limited slip additive , because they added it at the factory. What is right??
Add or Not to add??
Lariat#1

 

I bought it, basically because it was pretty cheap and for say so. I did get the additive also, why not right? No problems so far, maybe a year with it. Gear oil is very thick, very forgiving, so try it out with the additive (piece of mind) even if the stuff has it already in it.

 

I've used it in the motor, transmission, and rear end of all my vehicles for the last 5 years or so.

One of the first things I do when I buy a vehicle is replace all fluids and I replace them all with RP. It DOES in fact have the limited slip additive. I have used it on 2 of my personal Supras as well as quite a few race cars i helped build as well.

No extra additive necessary. Add the friction modifier if you want, but its not necessary. Waste of money to put it in there when it already has it, in my opinion.

 

Shortly after buying my '02 King Ranch, I replaced ALL the fluids, (rear axle, front axle, transfer case & tranny), with RP. I did not put anything else in with it. I have not had any issues what-so-ever since.

 

6,000 miles until I hit 80k, when I pour some in my differential.

 

Royal Purple is good stuff. I have used it without any issues. Nor have I ever heard of someone using Royal Purple, and having it cause a catastrophic failure.

 

I have RP in my transfer case and both differentials. I used it in the motor for a while. I didn't think there was enough difference between it and Mobil 1 to make the price difference worth it though. The transmission and PS system going to get RP soon.

 

I use the cheapest synthetic oil I can find. If it happens to have the additive in it then I do not add any friction modifier. Like it was mentioned; why pay for nothing?
I have about 200,000 (124,000 miles) of hard kilometers on my diff and so far it has held up. Honestly though, I think that it is rather a testament to the axle not the oil used.....

.

 

Any full synthetic 75W-140 will do the job fine. There isn't much difference between brands other than the lack/presence of friction modifier for LS.

 

i use RP because its top quality, and my yukon 4.56 werent cheap, so im using the best, and it already has the LS additive in it

 

RP's prices aren't that bad either.....wish I had access to more of their product line locally however

 

I add the friction modifier anyway

 

The additive is cheap, and for the potential pain in the a** of having it acting up and then having to add it anyway.....I'd do it while I'm already under there to begin with.

 

GIP1979 is correct about RP however.......i just tend to overdo everything! hehehe

 

I have RP in my rear diff, I dont think it did too much but haveing a good quality oil is a good thing. I didnt add the friction modifier