I was prepairing to change my diff fluids and contacted my dealship here in Anchorage. The Service Manager said I had to use the Synthetic Mopar fluid for warrenty reasons. When I asked why the owners manual said synthetic 75-90 he said there was a mistake and that I must use the Mopar oil. I wonder is it is that they get almost $30 a quart for it.

I really don't believe this to be true but would like to hear from anyone who can shed some light on the subject.

THX
AZ

 

It won't void anything that guys is just being an ***hole. As long as it has the same rating or higher you'll be fine.

 

As long as it is synthetic GL-5 75W90, it meets the specification in the factory service book...

My dealership sold me the Redline 75-140 that I'm running in mine.

 

I was told the same thing. I posted a question here on this topic and everyone said that the GL5 75-90 would be fine. However, my dealer said that I need the Mopar oil, so I bought it. Funny thing is that the bottle does not say anything about a special formulation that the dealer claims.
But in the end it is the dealers opinion and report that counts if I have to make a warranty claim. So $90 worth of fluid for each diff, at least until the warranty is up.