Oil for flat tappet engine.....2005 Jeep 4.0

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I know this subject has been beat to death, but it seems oil formulas are constantly changing.

I have been using QS Defy 10w30 in my Jeep Wrangler with the 4.0 6 cylinder engine, but I read that the ZDDP levels have been lowered.

What is a good oil to use in a flat tappet engine?
 
Low spring pressures mean you could run just about anything. the '98 4.0 in my sig called for 10W30 (in most temps) originally, but it seems to like 10W40 & 5W40, it's had syn 5W30, but the hot oil pressure was a little low. Even straight 30 or 15W40 would be fine. I believe that Defy 10W40 still has high ZDDP levels, around 1200 PPM, since 40 weight SN levels are higher than the lower weights-I've run it myself with good results.
 
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Your engine does not need extra ZDDP. Only flat tappet engines with increased spring pressure benefit from this. Stock engines can use any quality api sn oil.

According to some sources there may not have been a change in the defy formulation but Ratner just a new certification with the flirting of Max zddp limits on the old formula. I haven't seen the new voa yet so hard to say
 
My personal pick is for the 4.0 is Rotalla 10w30 or 15w40 depending on your climate. The tolerances are loose but as previously stated the low tension valve springs don't need a lot of ZDDP. 5w-30 tends to get consumed at a higher rate.
 
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Originally Posted By: fins

What is a good oil to use in a flat tappet engine?


I've got three Jeeps with the 4.0 engine, two '96s and a '98. My favorite of the three ('96 Cherokee with the 5-speed) is close to 300K miles using some of the cheapest oil I can find, including Smittys and Peak. If the engine is broke in, I wouldn't worry about your oil choices for the 4.0 engine.
 
Rotella T6 or that T5 blend 10W-30 is what I'd use. 15W-40 might be a little rough on the crank starting on a cold morning so it would be best to have a 5W or 10W in there just to be safe if it were me! Both the T6 syn and blends have nice pour points and are reasonably priced to boot.
 
My Jeep definitely seems to run quieter with xw40 weight oils. PYB 10w40 is one that I've had great luck with in terms of noise reduction and there's a few UOA's here showing pretty dang good results. Currently running 10w40 Castrol Syntec and have some Castrol Edge HM 10w40 for next time. Both are A3/ B4 oils. Somewhat comparable to T6, TDT etc. I'd say.

I run M1 TDT 5w40 in my dad's Renix 4.0, but it has just under 90,000 miles too.

In terms of startup noise, the #1 culprit seems to be the filter choice. Sadly, my Jeep hates WIX filters. I've tried the Napa Silver and Napa Gold. I used to have really good luck with the Mopar filters, but they turned out to be as noisy as a WIX. I always go back to some sort of Fram filter. With this run of 10w40 and the Ultra, I've experienced a few start up rattles, but the temps were just below 0*F. Doesn't get much colder than that here.

*I might give 15w40 a try in the summer. Run it from say April to September.
 
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Depending on your climate - 10W30 , 5W40 in the summer and 5W30, 10W30 in the winter . In my son's '03 Rubicon we have used Rotella T6 , Pennzoil and Quaker State 10W30 (synthetic)with good results . Tried M1 10W30 but for some reason a bit noisy in the Jeep 4.0 so I was one and done with that offering .

*This thread ain't over until KCJEEP chimes in ...
 
Originally Posted By: Chris142
Dont worry about the cam and lifters. They will be fine. Its the cam gear and opda in the 05 and 06 that are having trouble.



Replaced mine with one from Crown
 
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