Just wanted to let everyone know about my recent dabble with this oil. I changed oil In The 98 with the Quaker state defy 10w30 recently. Main reasons I went with it were price (3.49 at advance right now), and the higher zinc content ( look it up on bob is the oil guy). I can tell you that it's not a night and day difference but definately noticeable! The first was the slight valve tick was almost all the way gone. Btw: I always use 10w30 in this one. And the engine just seems to be a but smoother. Not sure totally how to describe it bit you know how your ride feels and it's definately feeling different, in a good way. At first I thought it was me but the GF ( who's jeep it is) said that she feels like its running better also. So just wanted to let everyone know about this oil and how it's performing so far on the 4.0!

Btw: I am not affiliated with advance or Quaker state! Haha!

What oil did you normally use?

......and how long had it been in?

I was normally using just regular castrol 10w30, I've probably got about 150 miles on the Quaker state, so not a huge amount but definately enough to get a few heat cycles on it. Always changed at 2900 miles ( don't ask me why it's just what I do!)

So, you're saying that changing to a different gimmick oil, same weight, that your Jeep runs dramatically better?

While I do back Quaker State, sounds as if you are basing this off a butt dyno.

Placebo effect

ill stick with penzoil high mileage or valvoline high mileage....run it in my jeep and in my truck and they always seem to run fine

I like the penzoil b/c of the "claim" it cleans out sludge


I highly doubt it cleans sludge...but in my head...everytime i start my truck or jeep, its cleaning the motor out little by little, and thats all that matters

This ^

You're takin tha sugah pills.

Fresh oil is (any oil) different than the old oil. I use wally world supertech 15-40 because it is the least expensive high zinc fleet oil that I have found. I am not brand loyal as long as it meets spec.

Whether it is just the result of good advertising or not, the important thing is that the OP feels and believes that it has improved the operation and performance of his XJ. in my mind that is a successful product. I think it is extremely difficult to determine whether or not the new Quaker state defy does actually stop future engine wear or not since you can't really judge significant wear between starts or without really tearing down to vital engine parts. it does have a higher zinc content which is very valuable from what I understand.

So I say this. Kudos to you on taking the plunge and the time to report your findings to us.

I stated in the first post that it is not a dramatic improvement. I really don't buy in to the gimic of stopping future engine wear. The point I was making was for an inexpensive oil it has a high zinc content which the jeeps seem to do really well with. And it's pretty readily available. The fact of the matter is engines wear and that's the way it is. Any claim from a company that it will stop engine wear I believe to be false. I totally agree that fresh oil feels different than old oil; however I have personally changed the oils in this jeep for the last 50000 miles and have definately grown accustom to the way it behaves after an oil change. Am I getting more horsepower? No. Am I getting better mileage? Maybe a smidge but probably not. Can I hear the difference in the engine? Absolutely and it is not a night and day as stated above just a smoother note and less valve train noise. But not dramatic.

Sorry to rant! Haha have a great day everyone!

Zinc is key. More the merrier.

Changing the oil every 2900 miles is a waste of time and money. Every 6000 miles is perfectly fine, you can even stretch it to 7500 miles depending on the type of driving you do. Mine gets changed every 10,000 miles wether it needs it or not.

Point taken. Almost bought this instead of rotella last week...probably would have been just fine. Thanks for the info, i haven't tried to find any data sheets on this oil yet. Cheers.