Royal Purple recommends the following for the JK:

Engine Oil: Royal Purple SAE 5W-20 (part #01520, quart bottle); capacity 6 quarts

Engine Oil Filter: Royal Purple #10-2835

Auto Transmission: Royal Purple Max ATF (part #01320, quart bottle); capacity 4 quarts for a pan drain and refill, or 8.8 quarts for a complete drain and ‘dry fill’.

Manual Transmission: Royal Purple Synchromax (part #01512, quart bottle); capacity 1.6 quarts

Transfer Case: Royal Purple Synchromax (part #01512, quart bottle); capacity 2.1 quarts

Differentials: Royal Purple Max Gear 75W-90 (part #01300, quart bottle); capacity 1.05 quarts for the front and 2.4 quarts for the rear

 

I would say thats a decent recommendation except the engine and transmission. I am a FIRM believer that changing those fluids is much better than putting a better fluid in it. I feel you'd get better longevity of your components by changing it more often with 'okay' products, than running it longer/harder with 'awesome/expensive' products.

As far as oils go, unless you're going for every horsepower from that 3.8L, the "race oil" is a waste, in my opinion.

I have mobil 1 synthetic in my axles, and have had royal purple in my tcase and manual trans (now Amsoil).

Just my opinion on fancy products in engines and transmixers.

 

how about going with the royal purple but still changing more regularly? Wouldn't that be the best care possible?

 

I'm no oil engineer. I think it's best suited for 'extreme' situations and all our horsepower. It's money down the drain in my opinion. But thats all it is.

 

That's what I do

 

X2


It might money down the drain. But until its proven that it's not helping my engine. I'll keep wasting money. Better safe than sorry.

 

Ran Mobil 1 in the engine since Day 1. Can't find them in a 5qt. bottle anymore so now I'm running Castrol SynTec. 5w20 since CryCo recommends it. Run Mobil 1 in the transfer case. Run Mopar in the transmission (it's takes lots of abuse, last thing I need is foreign fliud in it, besides, CryCo knows that fluid to run in their vehicles). Amsoil for the axles.

 

I drive about 50K a year in my company truck. We change the oil on the numbers and use the cheapest "ok" oil we can get in a 55 gal. drum. Company policy says we get new trucks at 200,000 miles and since I have been here (25 years) we have never blown an engine. It seems to me that when it comes to engine oil, frequency is better than quality.

Just my observation.

Dan

 

Has there ever been an independent testing and evaluation program done for oils (i.e. car and driver, peterson's 4x4, jp mag, etc...)?

Does Amsoil, Slick 50, or any other "magic oil" really provide a performance gain over your routinely available Mobil/Castro/Other 5w/10w/20/30?

Interested in the feedback...

 

Here's what I found:

"In July 1996, Consumer Reports published the results of a two year motor oil test involving a fleet of 75 New York taxi cabs and found no noticeable advantage of synthetic oil over regular mineral oil.[13] In their article, they noted that "Big-city cabs don't see many cold start-ups or long periods of high speed driving in extreme heat. But our test results relate to the most common type of severe service — stop-and-go city driving." According to their study, synthetic oil is "worth considering for extreme driving conditions: high ambient temperatures and high engine load, or very cold temperatures"
Granted the above study is from 1996...are there more recent tests out there?

I've always been a fan of Mobil 1 myself. I don't feel the cost difference is all that great, so for me I will continue to use it...with that said however, Consumer Reports is a very compelling organization...