Hello good ol trusty CF. I have came with a question that needs to be answered. Im due for an Oil Change and im thinking about switching it up a bit and changing to 10w-30 Royal Purple Oil. Is their any benefits or noticeable gains? i just know its 2x more than the rest of the oil.

On a side note im thinking about running Premium unleaded gas instead of regular unleaded.

PurpleKrawler needs to be spoiled!!

i would also like to hear responses on the differential fluid as well

no1?

I like royal purple for diff fluid. One of the main reasons why is because it doesn't smell nearly as bad as any other brand haha, seems like it holds up better too. As far as gas, the way it works with gasoline is that the different octane level has to do with the temperature and pressure that the gasoline combusts at. I know this is a very vague explanation, but a car that requires higher octane fuel requires it because it needs the gas to combust at a higher compression so by putting it in your xj it should give no benefit and would possibly be worse for your engine than regular gas due to not combusting soon enough. Get a fuel system cleaner instead such as seafoam.

I can't comment on the oil. I know royal purple makes good stuff (also look into amsoil), but I have no first hand experience, I usually just buy the cheapest synthetic deal and change it every 3500 miles.

Thank you very much

i run it every oil change and i like it alot, i dont know if it changes much but i know i can trust it

Just run plain old Rotella 10w30 in your 4.0. No need to shell out extra $ for fancy oil. If you can add more zinc and phosphorus your 4.0 will love you more.

what ever you do, don't run penzoil. That crap will turn to glue in your engin. your best bet is to run the same oil for the life of your car. changing oil brands is not good for it even if you are going to a better oil.
Don't put the high octain gas in because like said before you dont need it and it may make your engin run worse.

I haven't run any in my Jeep. Right now I use Mobile1 High milage. I have used RP in my 92 Nissan truck though and currently it's got 20-50 in it. I have also used Redline 10-40 in my Nissan.
What I can say about both those oils is they are good but different . I had lifter noise in the Nissan and did not want to tear it apart because it ran and still does perfectly. The heavier syn oils quited it down. Redline 10-40 quoted it down more than the RP 20-50 but for some unexplained reason was burning off or something and I have zero oil leaks on that truck, dino oil never had to add any nor with the RP. With the RP it is not as quiet as the Redline but I have yet to add any and it's got about 5000 miles on the change but mainly just sits as a back up vehicle right now.

i just used it in my transmission and it seems to cool it better

I use it in everything, feels like it runs a little smoother, but that could just be me. Although my temps stay about 5° lower on average. Also, Royal Rurple lasts a little bit longer.