Kymasabe

Actually, this isn't a "what's the best oil for my Jeep" question. Just a couple of quick observations I wanted to share. I'm currently experimenting with a couple oils to see what my wifes Jeep ('04 Grand Cherokee with 4.0) likes best. ( I know this is the XJ forum, mines mentioned next in next paragraph, hang in there !) I've been using Super-S 10w30 semi synthetic for a while, bought a ton of it cheap when K-Mart closed. I do oil changes every 2500 miles and use either Mopar or Napa Gold filters. Anyway, been researching and reading and decided to try some Valvoline MaxLife high mileage 10w30 this time and...noticed my motor is louder, more ticking with this oil. I dropped in a bottle of STP Oil Treatment to quiet it down again. Never had that problem with the Super-S, started immediately with the Valvoline. I'm not even sure the STP is good to use, but figured it had ZDDP or whatever that zinc stuff is that everyone raves about so...figured it can't hurt. Much. Or can it?

Next: Oil filter. for Napa Gold, I use the #1085 but just discovered today that the #1515 is same thread pitch but much longer filter. Am I the only guy here that didn't know that? Food for thought for next oil change.

Lastly. I was buying some oil today for my 1999 XJ that I'm buying in about an hour. Wanted good wear protection, maybe something high mileage,wasn't sure, heard good things about Quaker State Defy. I NEVER use Quaker State. I'm more of a Pennzoil guy but, decided to call Quaker State to ask some questions. They answer the phone as "Shell Oil" and the tech guys answer questions for Shell, Quaker State and Pennzoil. So, I told them year, make, make, model, told them I'm not looking for seal swellers as much as I'm looking for best wear protection and I couldn't decide between Quaker State or Pennzoil. Know what the tech assist guy says? Don't buy either, buy Shell Rotella T4 or T5 in 10w30 for the best protection. Hmmm. Interesting.

jordan96xj

I went through a noisy-oil experiment phase myself. My motor had about 50k miles on it. I had just switched to Rotella T6 and noticed that my motor was louder (not a lot, but I noticed it). So I tried Castrol GTX, Quaker State, Valvoline MaxLife, and Pennzoil Conventional High Mileage.

Ultimately, I settled on the Pennzoil (5w30 winter / 10w30 summer). It was quieter, decently priced, and almost always has a coupon going at my local Advance (one of those oil/filter detals). I decided to change on 5k intervals so that there is no confusion, I just change oil everytime my odometer hits the next 5k even (50k, 55k, 60k, etc.)

5-Speed

This is going to turn in to a typical oil thread. I hope you know that. But I will throw in some of my experiences too. I first put Castrol GTX 10-30 in. Found nothing wrong with it. I read the 1000s of oil threads that suggested diesel oil and at the next oil change, put Delo 400 15-40 in it. Oil psi was slightly higher but man did it make the engine loud. Sounds like piston slap now. Never made the same noise with the Castrol. My buddy put Delo in his XJ and it did the same thing. So needless to say, the Delo is getting dumped and I am going the Rotella route.

jordan96xj

True. I don't normally participate in these. But since OP wasn't really talking about favorites, but just a few observations, I figured I'd share what I observed as well. I'm sure I could have stayed with any of the oils I tried and been just fine. I don't really have a favorite. Pennzoil just happened to be the one I thought was the quietest at the time (which was pretty subjective to begin with). Because once you start thinking your motor is noisy, it is all you think about!

LadyKenai

ok, not really expert on this but just my experience. we used 10w30 for long time and just lately we used 10w40 from Shell and the engine runs more quiet, just did round trip for 1800 miles and almost ready for an oil change again and i will go with the same one from Shell.

marc

edit: and this is on our 94 xj with 288k miles

tech

I found the best oil for my xj is 10w-40 Mobil 1 . the engine is quiet and it doesn't use any oil and I have about 150,000 miles on it

00t444e

I run castrol 15w40 diesel oil. It brought oil pressure up by 5-7 psi over the 10w30 I was using. It was on clearance at Wal-Mart for $5 a gallon so I got 9 gallons of it. I use the same oil in my truck, lawn mower, and Yamaha Rhino too.

Kymasabe

Well, I bought Quaker State High Mileage 10w30. I have no idea why. Wasn't sure I trusted a "diesel" oil in my Jeep.
Then, about an hour later, I went back and was gonna buy the Rotella, but it's not SN rated and Delo is so...I bought Delo 10w30. Now I'm sitting here wondering if I've lost my damn mind as I've never bought either before and wondering if I should just return both and go with plain old simple Pennzoil like I've used for the last 2 decades. Why does picking the "right" engine oil have to be so difficult?

jordan96xj

Yeah, its a bit of a rabbit hole. The people that market the product know that as well, and they depend on it. Because once you pick one (for whatever reason makes you happy), there is a high degree of certainty that you will pick it again for some time to come. And most of this has little or nothing to do with what is in the oil.

Waynerd

I ran Quaker state high mileage years back in a WJ with a 4.0. Was only quiet until it was warmed up.
Recently ran half a quart of mystery oil added to 10-30. Wow was that loud. I ditched that as soon as possible and went with plain old Quaker state. Took a bit but finally quieted back down.
Also running Quaker state in another and it seems fine. Motor is quiet. Usually run T5 but idk if wal-mart is no longer stocking it or what. Only went with the Quaker State because of price and the fact that they didn't have enough Shell in stock. I usually buy enough to change in 2 Jeeps. Sometimes 3 but the 3rd doesn't get driven much.

s346k

rotella t6 all year. 8k OCI. done.

CobraMarty

Which oil? That's a huge book.

I've read all the articles, compared all the oils, tried many different oils, and in the end I make my decisions based on the following-

Wear Protection- film strength/load carrying capability/shear resistance measured under load at constant temperature, in psi

Zn and Phos- are both anti wear and work together, called ZDP, ZDDP, etc, Phos kills cat converters

Moly- anti wear additive, forms a layer on metal, very 'slippery', increases economy, will not poison cat converter

Ca- detergent, cleans sludge, too much is bad, it increases rate of decomposition of Zn and Phos.

Rotella T6- 67,804 psi, Zn-1264, Phos-1147, Moly-59, Ca-1066
Mobil 1 5-30- 105,875psi, Zn-801, Phos-842, Moly-112, Ca-799

So what do I use?
Especially on an unknown maintenance, new to me car-
-change filter and use most any dino oil 10-30 and add a can of Seafoam and run it 500-1000 miles, then
-change the filter and oil and use Rotella T6 for 1-2 oil change cycles, then
-change the filter and oil and use Mobil 1 5-30 and change every 10,000 miles

WHY?
I use the Seafoam as a base cleaner to clean the sludge and all
I then use the Rotella T6 because synthetic is best, and it has high Ca which is a detergent and continues cleaning, but it has lower psi rating and high Phos which kills cat converters
Lastly I use Mobil 1 5-30 because synthetic is best, and has over 100,000psi film strength/shear resistance, less Zn and Phos which kills cat converters, less Ca detergent and More MOLY, change every 10k.

Rotella T6 is a great oil, I use it, but has very high detergents which makes it great for diesel engines and will harm cat converters. Short term, 1-2 oil changes, will have the good cleaning properties and less negative effect.

Mobil 1 5-30 has less detergents, cat friendly, more 'slippery'. Has been my oil of choice since mid 70's when it first came out. I have never lost an engine using it. Recommended by most OEM manufactures in their high performance engines.

investinwaffles

I have used Rotella T6 5w40 for at least 60k miles at this point with only good results.
Inside if the motor and oil pan are very clean. It does make my lifters louder so I put in 1/2 bottle of Marvel's Mystery Oil which quiets it down a lot. Then I just add 50/50 T6 and Marvel's when I need to top up.

About 6K mile oil change intervals with a Wix 1515 filter and the 4.0 seems pretty happy about it.
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extrashaky

For those of you using 5W40 and saying it makes your valve train noisy, do you suppose that could be because not enough of the thicker oil is making it to the top end to lubricate it properly?

s346k

ive been using t6 for 100k miles. in my experience it has not made the engine noise any louder. if anything, honestly, it has made it quieter. an engine will be noisy with fresh oil. every car i've owned and used synthetic oil in (several) would be noisy for a week or so after an oil change. at 200k miles - for ****s and giggles - i sent a sample to blackstone for analysis. i forgot to include the info card. they guessed an engine having half the miles of mine and exactly 3/4 the miles on the oil sample. i guess it's doing all right. it has 230k on it now. it uses little to no oil on the OCI i am doing, it shows roughly 1/4 qt under full at 8k miles. gets 19-21 mpg religiously and still runs away from every other 4.0 i can find.

also - the only thing going in the oil pan is oil. monitor oil condition and shorten the oci as needed if it's got sludge in it. regular practice WILL safely clean the engine.