Oil Recommendation - 1999 Jeep Wrangler 4.0

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Hey, everyone. Looking for a recommendation on oil for my Jeep. Did a search but only pulled up one thread on a Grand Cherokee. I may have googled wrong. 1999 Jeep Wrangler 121 k miles Daily driver and some light off road, though when I get my next daily driver this will become an off road toy. I drive daily an average of 25 miles each way to work and back, mostly interstate. Head gasket leaks, has for about two years, hoping to replace the head in the next six months. Lifted 4 inches on suspension, 33" tires, Mustang fuel injectors, Borla performance exhaust with rebuilt exhaust. I try to drive easy as often as possible, though when I'm late for work all bets are off. Been using full synthetic Castrol edge titanium for six years. Normally 10w30, though sometimes 5w30 when I change in the winter. Bosch premium filter. Try to change every 5 months. Kentucky, temps get up.to mid nineties in the summer, teens in the winter. Temp can spike up to 100 and down to single digits. Is 10w30 the best weight to run for my conditions? I've been happy with the oil so far, but curious about any full synth options. Also curious about opinions on filter. Thanks for any input!
 
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Fix the HG leak first. Then try either the Mobil 1 0W-40, Pennz Plat Euro 0W-40, or Castrol Edge 0W-40. It will cover you on both ends of the environmental spectrum in KY, and those oils all have stout add packs to protect your engine.
 
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I'd say the 10w30 would work most of the year. I run that in mine till it starts getting lower than 32 or so. Here we get far below 0 and I run 5w30 then. But the 0w40 or even 5w40 would be great if you want something you can just stick with year round.
 

Mercury

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Subie: would if I could, just have to save up a bit for the $1k repair cost. Would you tell me why the Pennzoil Euro is your choice? I'm looking at it in the store and I see it's designed for, surprise, European cars. Hoosier and Subie: I was thinking about trying 5w30 for year round, but 0w40? Not disagreeing, just curious why that weight for year round. Of course this store doesn't have my beloved Castrol edge in anything 40
 
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i ran napa 10-30 and or 10-40 dino in mine for well over 400K. and i was never easy on it. it's still driving around town today. i changed the oil ever 5000-7500 miles and used fram TG filters. these are great engines. get good plugs in it, fix the HG, it's an easy job, should only take you about 1/2 day to a full day. change the coolant when it should be as well.
 
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I also have a 1999 TJ and live in Kentucky. I run PP 10W-30 year round. After 15 years of ownership I see no reason to change...
 
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Make sure your Jeep doesn't have the 0331 cylinder head. A '99 Wrangler probably doesn't, but Jeep never did follow strict orders, so if you have a late '99 with the 0331, replace the whole head with a TUPY replacement that has a less tendency to crack. As far as oil recommendations, the 4.0 oil recommendations have been beaten to death here lately.
 

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Killer: I know just enough to get myself into trouble. If I had a garage to work in I'd try the swap myself. I figure that since I'm doing the work I may as well put a new head in. $450 at auto zone. Seems like a good price. Want to put in an early 90s H.O. head to let the bigger fuel injectors and larger exhaust manifold get more use. Compact: that's awesome. If you drive around Louisville I may have waved at you. Kruse: I had no idea, and thank you for that advice. I'm not sure how to check that but I'll Google in a bit. I figured it was a common question, but when I searched for "Jeep" it only pulled 200 results with one thread about oil. May be because I'm doing this on my phone, but my laptop went down recently so it's all I have. If you get a sec could you link one? Search still isn't pulling anything for me.
 
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I am assuming you have the 4.0 They run hot. Get a Scangauge or Ultragauge to really monitor water temp. Dash gauges lie above 210F. Make sure the cooling system is healthy and the coolant is good. Overheating will crack the head and/or head gasket. I run pretty much any synthetic XW30 or XW40 for 5000 miles with a Fram Ultra XG8A
 
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Originally Posted By: Mercury
I figured it was a common question, but when I searched for "Jeep" it only pulled 200 results with one thread about oil. May be because I'm doing this on my phone, but my laptop went down recently so it's all I have. If you get a sec could you link one? Search still isn't pulling anything for me.
My apologies for my post. It was late and I had a long weekend. The 1999-2000 model year 4.0 Jeep engines could have the 0630 or the 0331 cylinder head. Your engines SHOULD have the 0630 head, but Jeep could have started using the 0331 head about the time your Jeep was manufactured, or perhaps somebody put an 0331 head on since it was manufactured. (A lot of years have passed since it came out of the factory) The 0331 head has a tendency to crack even if it was never overheated. If you are going to change the head gasket, I would replace it with a TUPY head, reportedly a revised version that resists cracking. (But that's just my opinion, I don't like to do a repair twice) Jeep of that era like to run warm, but it's usually the Cherokees that are the problem child because of the design of the radiator. As far as engine oil, just about any good 5W-30 oil will be good for your 4.0 and a 10W-30 will also be fine, especially in warmer states or for the summer. Your lifters will probably be noisy, usually nothing to worry about, and the 4.0 engine has a reputation for leaking oil, especially about the rear main, the valve cover and sometimes around the oil filter area. As long as you know that Jeep don't have the best reliability reputation and you can live with that, enjoy it and have fun.
 
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Originally Posted By: Mercury
Hey, everyone. Looking for a recommendation on oil for my Jeep. Did a search but only pulled up one thread on a Grand Cherokee. I may have googled wrong. 1999 Jeep Wrangler 121 k miles Daily driver and some light off road, though when I get my next daily driver this will become an off road toy. I drive daily an average of 25 miles each way to work and back, mostly interstate. Head gasket leaks, has for about two years, hoping to replace the head in the next six months. Lifted 4 inches on suspension, 33" tires, Mustang fuel injectors, Borla performance exhaust with rebuilt exhaust. I try to drive easy as often as possible, though when I'm late for work all bets are off. Been using full synthetic Castrol edge titanium for six years. Normally 10w30, though sometimes 5w30 when I change in the winter. Bosch premium filter. Try to change every 5 months. Kentucky, temps get up.to mid nineties in the summer, teens in the winter. Temp can spike up to 100 and down to single digits. Is 10w30 the best weight to run for my conditions? I've been happy with the oil so far, but curious about any full synth options. Also curious about opinions on filter. Thanks for any input!
welcome Agree with your use of 10w30. I had 00 and 04 Grand Cherokees with the 4.0 and used 5w30 most of the time, and 0w30 for several years in northern Montana (night temps down to -30°F). Living in the south I'd have been fine with 10w30 year round. You could have the 0331 head....look through and behind the exhaust manifold to see the casting number. If it's "0331" the metal used was substandard and becomes porous around 80-90k, causing coolant to mix with oil and in some cases, a cracked head. While this is happening I'd suggest (as did Blackstone and all my research when I had my 00) keeping your OCI to 2500 miles or less. Here are a few references, Googled with "0331 bob is the oil guy": https://bobistheoilguy.com/forums/ubbthreads.php/topics/2754216/1 https://bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=868549 https://www.cherokeeforum.com/f59/question-0331-head-211862/ http://www.jeepforum.com/forum/f11/what-s-best-inexpensive-way-replace-0331-head-699744/ Hope those are helpful. edit: oh, and one of the links goes to an explanation of the TUPY head that Kruse mentioned. thumbsup
 
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*Any* year 4.0 will warp or crack the head if overheated. They do not blow the head gasket 99% of the time. But you're planning on switching the head, so that's good. Also - people really like to overthink oil for these engines. They do NOT need high zinc oil. Maybe when it was new 18 years ago, but even then, there's not enough valve spring pressure to wipe lobes ... and it's not a 70s small block chevy. Run ... oil ... Mine has been getting supertech 10w30 synthetic year round. Once a year changes so about 6500 miles. Mine has hard use. I'm not big into mud, but I have no problem letting the 4.0 bounce off the rev limiter for minutes on end in the mud, or pull a trailer with it in 2nd gear on the highway. Or rock crawling all day at idle in low range 1st gear. It's only slightly tired but that's more from having >200K. But it's happy!
 
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Out of curiosity, what does the owners manual recommend? I am running 15w40, 10w40 and 5w30 in all my stuff. I am uncomfortable with any oil that starts with "0". But this has no logical basis. It's just me.
 
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I use Pennzoil conventional 10w30 and 5w30 in my Jeep. Many Jeep 4.0 owners have reported the engine runs quieter on the Pennzoil with the high moly content. I have a Used Oil Analysis from mine, and had single digit iron wear numbers. The 4.0 is known to have higher iron numbers, so the Pennzoil did well (see link below). Jeep Cherokee 4.0L used oil analysis
 
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Sis' 1999 XJ sold 5 years ago with 171K. Didn't use oil. Quiet runner. Still in use today. I used Super Tech (Walmart), Texaco, Shell (from Costco) and the like....all 5W-30 conv. oils. I have a picture with the valve cover off and it is a cleanie. Wish I could post on this board. I used Hastings, WIX filters.
 
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I wouldn't go below 10w30 until -10F in this engine. The fractional MPG gain isn't worth the the added margin it gives when the engine gets sick.
 
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This is a good choice - a 10W synthetic is good down to 0 F. so no worries in KY !
Originally Posted By: MCompact
I also have a 1999 TJ and live in Kentucky. I run PP 10W-30 year round. After 15 years of ownership I see no reason to change...
 
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Originally Posted By: Mercury
Would you tell me why the Pennzoil Euro is your choice? I'm looking at it in the store and I see it's designed for, surprise, European cars. Hoosier and Subie: I was thinking about trying 5w30 for year round, but 0w40? Not disagreeing, just curious why that weight for year round.
Mercury, some of the guys here are Castrol or Mobil 1 0W-40 fans; I have no problems with either of those oils, but I prefer the PP Euro now. I have a UOA posted here on the board from my 06 Odyssey with this oil, and the Honda J35A7 is known for being hard on oils. My wear metals were really low, and at 7,650 miles the TBN was still 6.0. This oil also has healthy doses of antiwear elements (moly & boron), and is good on ZDDP for your older 4.0 as well. The 0W properties will make it fine in cold weather, and the 40 weight will ensure that even in the summer you will have enough oil film strength. To me, all of these things coupled with the fact that 5 quarts is only $22.97 at WM makes the choice a no-brainer. For reference, the 6.5k sample @ 146k was Pennz Platinum 5W-20, after a 3.5k run on PP 5W-20 to flush out the unknown oil sample at 136k. Chris
 
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