How many miles on RP gear oil?

Does anyone know how many miles you can go on royal purple gear oil 75-90? I know with the non synthetic they recommend 30,000 but I have looked everywhere and can't find any recommendation for synthetic RP.

I'm wanting to go RP from front to rear over time. I know it's more expensive but I want a good oil so the truck will last. I want to join the million mile club with this truck. 50 K down 950,000K to go.

 

I use Mobil 1 full synthetic in everything (except the manual trans-Red Line MT90 there), but I still replace them at recommended intervals or sooner, depending on use. This gives me a chance to analyze the oil. Even though the cost is higher, the reduced friction and wear make it worth it to me overall. I know this is overkill, but I use my trucks hard and like you, I want them to last as long as possible. Just my .02

 

I replaced my rear diff oil with mobile one at 60 K I think it was so long ago I'm at 127 now probably due again

 

15k is an easy interval to live with...I just use the five gallon bucket with a pump.

 

Wow! You have high hopes for your truck.

950,000K = 950,000,000

 

I stick to manufacturers recommendations regardless of the type of oil I put in.

 

5 year old truck with 50k miles, should only take him about 95,000 years. XD

 

I'd say every 30k for the diffs. Thats when i do mine.

 

I guess I will get my money's worth out of it.

 

Do it at 30k.

I changed my rear diff on my new truck at 6k total miles and it was disgusting with all the break in wear.