View Poll Results: Best oil for 60,000 mile 4.0 I-6.

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  • Conventional oil.

    25 28.09%
  • High mileage conventional.

    10 11.24%
  • Synthetic blend.

    7 7.87%
  • Full synthetic.

    36 40.45%
  • Extended performance full synthetic.

    4 4.49%
  • High mileage full synthetic.

    7 7.87%
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Thread: Best motor oil for 4.0 I-6 engine?

  1. #1
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    Default Best motor oil for 4.0 I-6 engine?

    What do you guy's recomend for a 60,000 mile GC that has run conventional oil up until now?

  2. #2

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    Just buy some oil and put it in.... I run the cheapest stuff I can find at the local Canadian tire store, 236 567K as of today , still going strong.

    99WJ I6

  3. #3
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    Where is FastSUV??? Another oil thread for you...
    1997 JGC Laredo 4.0 4x4 81300mi
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    Quote Originally Posted by Billy Ray View Post
    You should remember that some of the most opinionated and self proclaimed 'experts' on this board are really 16 years old and their “built' jeep is their yuppette soccer-mommy's totally factory stock vehicle complete with Baby On Board and Green Peace stickers that they only get to drive it to the library or mall on the weekend if all their homework is done and they've eaten all of their Brussel Sprouts and Lima Beans.

  4. #4
    MY JEEP > YOUR JEEP KMHogan224's Avatar
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    Quote Originally Posted by guthycs View Post
    Where is FastSUV??? Another oil thread for you...
    Or BillyRay for that matter.

    Come on man, there are SO many threads about FREAKIN oil. JUST SEARCH!!

    It's all opinion. Personally, I run nothing but Castrol Fully Synthetic oil. I don't have time for anything other than Castrol.
    '04 Blue Jeep Grand Cherokee Special Edition. IRO 5.5" Long Armed. 32" STT M/T's. Carolina Driveline Front DS. Rubicon Express Mono-Tubes. JKS Quick Disco's. 1.25" Spidertrax. Projectors. CAI, Tint, and Alpine/Kicker Audio.

    '04 Stone White Jeep Grand Cherokee Limited 4.7 H.O. Stock. 245/70/17 SilentArmor AT's


    Quote Originally Posted by Billy Ray View Post
    Finally: Be aware that most of the experts on this forum are 16 years old and their 'built Jeep' is actually their soccer-mommy's factory stock Honda Minivan complete with Baby on Board and Green Peace stickers that they only get to drive to the library after they've cleaned up the last of the lima beans on their plate.

  5. #5

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    since the 4.0 is prone to rear main leaks, I'd say conventional oil...BUT you give all these choices without more info. We need to know exactly how long you want to go between changes. The ONLY good reason for full-syn is to go extended service intervals. If you plan to change every 3-4k miles, then just get conventional OR syn-blend if you get it for a better price like I do. I use syn-blend because I get it cheaper per case at Sam's Club than conventional oil costs per case, BUT, it did make my existing oil seepage a little worse as compared to conventional oil. I change mine on my WJ every 4k.

  6. #6
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    It's not the oil that protects the engine - it's the frequency at which you change it.

    If you change every 3-5k miles then a brand name conventional if fine. It's hardly a highly stressed, high revving engine.

  7. #7
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    Quote Originally Posted by KMHogan224 View Post
    Come on man, there are SO many threads about FREAKIN oil. JUST SEARCH!!
    Did that, twice.

    Server timed out.

    Maybe need a better server?

  8. #8
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    Quote Originally Posted by FastSUV View Post
    since the 4.0 is prone to rear main leaks, I'd say conventional oil...BUT you give all these choices without more info. We need to know exactly how long you want to go between changes. The ONLY good reason for full-syn is to go extended service intervals. If you plan to change every 3-4k miles, then just get conventional OR syn-blend if you get it for a better rice like I do. I use syn-blend because I get it cheaper per case at Sam's Club than conventional oil costs per case, BUT, it did make my existing oil seepage a little worse as compared to conventional oil. I change mine on my WJ every 4k.


    OP assumes normal oil change interval of 3-4 K, and normal driveing habits for an adult owned vehicle.

    So you're saying the only bennifit of full syn is longer intervals? What about claims of decreased sludge/coke in engine and less wear..........just marketing BS?

  9. #9

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    Quote Originally Posted by FastSUV View Post
    s...The ONLY good reason for full-syn is to go extended service intervals. If you plan to change every 3-4k miles, then just get conventional OR syn-blend if you get it for a better rice like I do....
    x2

    I run Castrol GTX 5w-30 year round - change my oil every 4K miles

    I have no plans on switching to synthetic or even a blend

    My local Advance Auto Part sometimes has sales on Castrol GTX - can usually get 12 qts for about $22.50

    Quote Originally Posted by Bustawrench View Post
    ...
    So you're saying the only bennifit of full syn is longer intervals? ...
    Pretty much
    2003 WJ 4.0 3" IRO d30/d35 LR

    Quote Originally Posted by FischInAJeep
    The level of unsolicited braggardry (new word ; write it down) on these forunms astounds me.

  10. #10
    4 Litres of Fury trail rated's Avatar
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    Search BITOG (bobistheoilguy.com)

    I use shell rotella T 5W-40 full syn



    The 4.0 likes high zinc and high moly, which is what this oil has
    |2001 WJ|4,0L|42RE|NV 242|380000 km|ECE Compliant|
    Внедорожник для Экспедиций и Приключений

  11. #11

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    That is an excellent motor oil choice for a 4.0 L I6 with a flat tappet cam.

    For those of you who do not run a synthetic find a non energy conserving oil. This is better suited for your flat tappet cammed engines. Read the label, most of todays oils are energy conserving, this is not the best choice for a 4.0 engine.

  12. #12

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    This is my favorite quote about the 4.0 and motor oil (from another jeep site):

    its a 4.0. the technology in this motor dates back to the 20s. itll run on corn starch.
    The motor has been refined so many times it doesnt matter what you put in it (aside from corn starch). There are plenty of 4.0s on the road with 100, 200K+ miles on it which have run anything and everything from conventional oil to full synthetic. Pick a quality oil, change it frequently, and watch for signs of oil/engine problems. If none, you are good to go.

    Anyone have the link to that pdf on motor oil? Its the one that is 100+ pages long and goes into great detail about motor oil, testing, etc etc. I thought I bookmarked it but cant seem to find it.
    2003 WJ 4.0 3" IRO d30/d35 LR

    Quote Originally Posted by FischInAJeep
    The level of unsolicited braggardry (new word ; write it down) on these forunms astounds me.

  13. #13
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    Quote Originally Posted by trail rated View Post
    Search BITOG (bobistheoilguy.com)

    I use shell rotella T 5W-40 full syn



    The 4.0 likes high zinc and high moly, which is what this oil has
    Two questions..................

    1) This oil appears to be primarily designed for Diesel engines in commercial trucks..............

    http://www.sopus-staging.com/staging...ic_TDS_v10.pdf

    ..........why would it be better than Mobil 1 or Castrol Syntec in my 4.0 GC?

    2) Jeep specs out 10-W-30 for this motor...........why would I go to a 5-W-40?

    I'm in southern NJ so average winter temps don't get much below 30*F more than one or two weeks a year. Summer temps may hit high 90's four to eight weeks a year.

  14. #14

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    Here's a great article on flat tappets and Zinc/Phosphate - you'll first notice its from Hot Rod magazine...

    http://www.hotrod.com/techarticles/e...ech/index.html

    It actually hits on some points made by Vanquish above

    For our jeeps, though, high amounts of ZDDP is probably not necessary - our engines are neither high performance engines requiring such motor oil nor are they old enough to warrant such motor oil use (which would address older engine technology)

    Could you use such motor oil? Sure. Will you gain anything? Probably not much.

    However, I'm always keeping an open mind when it comes to motor oil - I would switch in a second if someone can provide evidence that products like Rotella will really extend my engine's life. However, when we have engines running for hundreds of thousands of miles on conventional or your typical synthetic, its hard to say that those high ZDDP products are worth it
    2003 WJ 4.0 3" IRO d30/d35 LR

    Quote Originally Posted by FischInAJeep
    The level of unsolicited braggardry (new word ; write it down) on these forunms astounds me.

  15. #15
    4 Litres of Fury trail rated's Avatar
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    Quote Originally Posted by Bustawrench View Post
    Two questions..................

    1) This oil appears to be primarily designed for Diesel engines in commercial trucks..............

    http://www.sopus-staging.com/staging...ic_TDS_v10.pdf

    ..........why would it be better than Mobil 1 or Castrol Syntec in my 4.0 GC?

    2) Jeep specs out 10-W-30 for this motor...........why would I go to a 5-W-40?

    I'm in southern NJ so average winter temps don't get much below 30*F more than one or two weeks a year. Summer temps may hit high 90's four to eight weeks a year.
    1) The 4.0 uses a similar design to diesel engines. This oil meets API SM (for gas engines) and API CJ-4 (for diesel engines).

    2) It's a long story and I don't feel like explaining it to you. The 4.0 was actually ment to run on 15w-40. All that 5w-40 offers is superior cold start and high temp protection.


    The 4.0 uses an old 1970's design and has flat tappets. With flat tappets, you need higher zinc, moly, and viscosity.
    |2001 WJ|4,0L|42RE|NV 242|380000 km|ECE Compliant|
    Внедорожник для Экспедиций и Приключений

  16. #16

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    Quote Originally Posted by trail rated View Post
    ...


    The 4.0 uses an old 1970's design and has flat tappets. With flat tappets, you need higher zinc, moly, and viscosity.
    Wait - did you just basically say that the 4.0 in my 2003 WJ is the same engine as that of the 1970s? No refinements made over the last 30+ years?
    2003 WJ 4.0 3" IRO d30/d35 LR

    Quote Originally Posted by FischInAJeep
    The level of unsolicited braggardry (new word ; write it down) on these forunms astounds me.

  17. #17

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    Quote Originally Posted by Bustawrench View Post
    OP assumes normal oil change interval of 3-4 K, and normal driveing habits for an adult owned vehicle.

    So you're saying the only bennifit of full syn is longer intervals? What about claims of decreased sludge/coke in engine and less wear..........just marketing BS?
    Syn oil IS better in every way. But it would probably take 400k miles to notice a difference on internal engine parts between conventional changed every 3k & syn changed every 6k....I use Mobil-1 full-syn in my ZJ (because that is what I chose 110k miles ago & stuck with is so far).

    The base-stock being syn or conventional means less than the additive pkg. Syn doesn't clean better, it's just that many syn oils are expensive & have a better additive pkg with more detergency. This still doesn't mean crap unless you want to push it longer on your oil change interval.

    Here are some things to know:

    1.) Syn is better at lubrication; especially at VERY cold or hot temps. It is better for use in a severe duty vehicle or someone who lives in extreme conditions and doesn't have a block heater, OR for race cars. But an avg joe doen't NEED syn if he plans to change the oil on time. If he chooses it, then great, it is newer technology and over many, many miles it may produce slightly less wear under NORMAL driving conditions.

    2.) It is a cost vs. benefit analysis. I am very anal with my vehicles, but I am also kinda cheap. I can't justify the price of syn unless I plan to go longer oil service intervals. But since I am so anal, I like to change it on time so I just use syn-blend for a nice price or Castrol GTX 10w30.

    3.) Don't get into the oil question too far or you may lose your sanity. I have obsessed about oil for 10 yrs. until I decided I was not an engineer and as long as I used a good oil and kept it changed I could move on with my life.

    4.) EVEN WITH syn oils, you are still limited by the oil filter. So for example, if you chose to use Amsoil (arguably best syn oil made), they recommend some crazy service interval like 10 or 12k miles. BUT they still want you to change the oil filter in the middle of the interval because the oil filter media gets clogged after 5-6k and hen it doesn't matter how good of oil you use, the filter will still get clogged. I recommend WIX filters.

    5.) Many 4.0 owners report long life and the ONLY consitency seems to be they changed the oil every 3-5k tops EVERY time.



    Quote Originally Posted by trail rated View Post
    Search BITOG (bobistheoilguy.com)

    I use shell rotella T 5W-40 full syn


    The 4.0 likes high zinc and high moly, which is what this oil has
    yeah the diesel oils always seem to be popular with the 4.0 due to the non-roller cam shaft. They also have super high detergency properties. I just never could get myself to make the switch since plain-jane oil is cheap & works okay if changed regularly. But yes, I wish I knew for sure if there were any plain-jane oils out there that also had the high zinc & phosphorus.


    Quote Originally Posted by Bustawrench View Post
    Two questions..................

    1) This oil appears to be primarily designed for Diesel engines in commercial trucks..............

    http://www.sopus-staging.com/staging...ic_TDS_v10.pdf

    ..........why would it be better than Mobil 1 or Castrol Syntec in my 4.0 GC?

    2) Jeep specs out 10-W-30 for this motor...........why would I go to a 5-W-40?

    I'm in southern NJ so average winter temps don't get much below 30*F more than one or two weeks a year. Summer temps may hit high 90's four to eight weeks a year.
    1.) yes but it will work nice in the 4.0 supposedly...not sure of the cost though.

    2.) 10w30 seems to be the favored choice, but except for Mystic, I am not sure of any diesel oils that come in 10w30. 5w40 would be fine in NJ though I'm sure, but I am still going to defer to Castrol GTX 10w30 & a WIX filter.

  18. #18
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    Older than that if my information is correct - started life in about 1964 or 1965. Lots of updates to the ancilliaries since then of course but basically the same engine.
    Most manufacturers don't like producing new designs of engines - they are too expensive.

  19. #19

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    Quote Originally Posted by FastSUV View Post
    ... & a WIX filter.
    Which WIX filter are folks using?

    I finally found a place near me that may stock them - will check them out tomorrow. I've been using Mobil 1 filters but if Wix is that much better I'd be willing to switch

    Any oversized WIX filter I can use?
    2003 WJ 4.0 3" IRO d30/d35 LR

    Quote Originally Posted by FischInAJeep
    The level of unsolicited braggardry (new word ; write it down) on these forunms astounds me.

  20. #20
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    Quote Originally Posted by OffRoadFury View Post
    Here's a great article on flat tappets and Zinc/Phosphate - you'll first notice its from Hot Rod magazine...

    http://www.hotrod.com/techarticles/e...ech/index.html

    Interesting article, thanks for the link.

    Brings up two interesting points against using the Rotella, however..........


    1) The additive package can be damaging to catalytic converters and O2 sensors.

    2) The amount of ZDDP is being reduced to eventual phaseout, beginning in 2007, the reason given being that Diesels are moving forward to required catalytic converters.
    Grease is cheaper than steel.

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