any problems with running 10w40 oil?

Not sure what any of the hard-core oil folks will tell you but 10w40 used to be the standard of what we ran in ALL our rigs for years. The Jeep is the first I've had that called for 10w30, followed by our Subaru which wants 5w30. Jeep is an '05, Sub is '07. With the ZDDP level issues for our engines, I talked with the guys at Royal Purple and they said NOT to add anything to the oil, but instead recommended I switch to 10w40 as it by allowed government specs to have higher ZDDP levels due to weight. They said to switch to 10w40 and not worry about a thing. I did, and have had no issues to date on the current fill, but again, it's been recent and I doubt I have 3000 miles on it yet. I've noticed no difference in running-other than it is a titch quieter, no difference in oil pressure on our dummy guage, no other engine related issues at all. Again, too soon for long term results...

Best of Luck,

Mike

Hey guys and girls, I spent a lot of time trying to find the best oil we can run in our flat tappet 4.0 engines. I went into the Corvette forum and several others and also several jeep sites. A lot are recommending the VR-1 Valvoline racing oil as it states not for street use, because it has the right Zinc amount in the oil it can't be sold for street use. that's how Valvoline gets around the Zinc additive they add to it. I have always changed my oil at 3,000 or more often when rubi sits during the winter. I always felt with 3,000 or shorter oil changes the regular good quality 10-30 oils would probably be ok. With the amount of cam problems increasing on all flat tappet engines with the low zinc content present in the oils these days I've changed my mind on this. Some are running Shell Rotella which is a diesel oil to get a good zinc level in the oil. This was made for diesel motors by Shell and has a good zinc content. You can always buy a zinc additive for the oil you use, but why pay the xtra $. and the hassel to order and stock. I'm going to change over to Valvoline VR-1 10-30 and see what happens. Some say the Zinc may cause premature converter problems, who knows? I'd rather have to replace my cat then my cam and lifters or possibly the motor due to metal contamination. Looking to make the old flat tappet out last me.
Ron

MPETE said:

I think this got missed so I am posting again.
so kaiserjeep, are you saying I SHOULD NOT run the 10w40 because of the additives, or should I just make sure I run seafoam a lil more often to clean out those deposits ?

thanks in advance

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I actually think that you can run any grade of oil authorized in the TJ Owner's Manual, which is any multigrade oil with A specified SAE viscosity rating and an API Quality Classification. MOPAR specifies that 5w-30 is "preferred" for 32 degrees F and below, and 10w-30 is "preferred" for 0 degrees F and above. "Preferred" in this case means that these are the grades that maximize fuel economy.

10w-40 is a non-preferred grade that will cost you a bit of fuel economy because it will be thicker than 10w-30 when the engine is hot. It will also make more carbon when your engine is mildly ill and burning a bit of oil, because of the higher amount of multi-viscosity clay additives.

I pretty much follow the MOPAR reccomendations for the first 100,000 miles. In California's mild climate, I run 10w-30 all year. Where I depart from the MOPAR reccomendation is when the engine goes above 100,000 miles. Then I switch to 20w-50 because I think it restores some lost oil pressure and clings to worn bearing surfaces better. Just something my old man taught me - he started running the AMC I-6 engines in the 1960's in Rambler automobiles.

As for Sea Foam, I DO NOT run it or any other additive intended to loosen or remove carbon. Firstly because I believe that any such additive is totally useless for the stated purpose. Secondly, if the additive were to ever start to work as described, then both the pre-cats in the manifold and the rear catalytic converter would be destroyed by the loose carbon. I believe the only way to remove carbon is to remove the cylinder head and use scrapers and abrasives. I also believe that such is only necessary when carbon has built up to the point where pinging happens and the engine diesels after shutoff.

The dieselling only happens on carbureted engines, so that symptom is only found on older Jeeps. But if your engine pings and you can't stop it by buying the next higher grade of fuel, time to disassemble the head and remove the carbon, in a safe procedure that will not destroy the converters.