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#1058848 - 01/06/08 01:11 PM 10w40 in the jeep 4.0?
lars11 Online   content


Registered: 12/16/06
Posts: 724
Loc: Sweden
Have been runnnig castrol 5w40 and Agrol 0w30 lately and it runs well on both. Then I have come across some posts here that says the 4.0 may be better off not runnning full synthetic.
Well, I can find 10w40 semi synthetic API SL/CF quite cheap. Would this be a better choice? Maybe in the summer or? The manual says any API 10w30, so I interpret that like I can do almost what I feel like. The engine is 2002 and has 50k miles on it.

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#1059010 - 01/06/08 04:55 PM Re: 10w40 in the jeep 4.0? [Re: lars11]
Greaser Offline


Registered: 02/13/03
Posts: 1992
Loc: Windsor,Ontario
To tell you the truth the 4.0L engine will run on just about any oil and be happy.The thicker 30 and 40 weight oils brought the iron numbers down in UOA's.That 10W-40 semi-syn you are talking about would probably be fine.The trick is REGULAR oil & filter changes in any motor.Used oil testing is the only true test of how any oil is behaving in your engine.Go to the oil testing forum and search for the Jeep 4.0L...mines in there and both my Jeeps like Esso XD-3 0W-40.
_________________________
1999 Jeep Cherokee-
2001 Jeep Wrangler- both engines 4.0L & Rotella T5/T6 with Napa Gold Filters

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#1059045 - 01/06/08 05:56 PM Re: 10w40 in the jeep 4.0? [Re: lars11]
Triple_Se7en Offline


Registered: 12/04/04
Posts: 6372
Loc: 1/2 hr. north of Detroit
5W-30 for your southern Canada winters - then 10W-30 from April thru mid-November.


Edited by Triple_Se7en (01/06/08 05:57 PM)

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#1059207 - 01/06/08 08:37 PM Re: 10w40 in the jeep 4.0? [Re: Triple_Se7en]
KW Offline


Registered: 09/04/03
Posts: 1685
Loc: Central Arkansas
I run synthetic 10W40 in my 1998 4.0 Jeep, with about 130,000 miles on it, for about seven years now with out and issue. It even had a rear main seal weep that went away after going to the synthetic 10W40. So I'd say stay with the Castrol 5W40 that you have been using in it.

I like the 40 weight in because it seems to run smoother and quieter when fully warmed up.

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#1059214 - 01/06/08 08:47 PM Re: 10w40 in the jeep 4.0? [Re: lars11]
Durango Offline


Registered: 02/15/07
Posts: 2045
Loc: Los Angeles, California
 Originally Posted By: lars11
Have been runnnig castrol 5w40 and Agrol 0w30 lately and it runs well on both. Then I have come across some posts here that says the 4.0 may be better off not runnning full synthetic.
Well, I can find 10w40 semi synthetic API SL/CF quite cheap. Would this be a better choice? Maybe in the summer or? The manual says any API 10w30, so I interpret that like I can do almost what I feel like. The engine is 2002 and has 50k miles on it.



lars11,

I've been using synthetic in my Toyota since bought new back in 89' With about 230K on the engine now it running pretty darn good in my opinion! Oh sure it burns/consumes a 1/4 quart in a month but it's longevity is most definitely contributed to the superior oil. Use a conventional in your Jeep I couldn't say if the engine will be in the same shape as mine.

Durango

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#1059328 - 01/06/08 11:26 PM Re: 10w40 in the jeep 4.0? [Re: Durango]
Gary Allan Offline


Registered: 09/28/02
Posts: 39806
Loc: Pottstown, PA
Well, lars, I run 0w-10 and 0w-20 in my jeeps. They're highly additized .so Keep the fuel system in good shape.

there you have it. A full spectrum of offerings. Clear as crystal if you ask me.
_________________________
http://lube-direct.com/gallan/

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#1060070 - 01/08/08 09:04 AM Re: 10w40 in the jeep 4.0? [Re: Gary Allan]
lars11 Online   content


Registered: 12/16/06
Posts: 724
Loc: Sweden
Gary, why the light oils? One problem with this would be that I haven't even seen any 0w10 in the stores and 20 weightsa are very rare here.. The 0w30 pumps well enough but a full PAO, it is much more expensive than the regular 5w40 syn that most people use here.

About the fuel system, anything particular to look out for? I use cleaner in the fuel from time to time. Anything else?

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#1060197 - 01/08/08 12:31 PM Re: 10w40 in the jeep 4.0? [Re: lars11]
Gary Allan Offline


Registered: 09/28/02
Posts: 39806
Loc: Pottstown, PA
Lars, I don't expect you to use lighter oils ..but I just do it to prove (or not) that viscosity isn't a mandate for long engine life. You won't find 0w-10 oils anywhere. 5w-40 is fine for this engine family. I've even used conventional 15w-40 my subfreezing winter (son's 4.0) without any symptoms other than fuel economy differences in shorter trip usage. Many of our membership have splendid UOA results with conventional 10w-30 oils as well.

I recommend doing a UOA to determine fuel dilution. Some suffer more than others. It depends on how clean your fuel is.
_________________________
http://lube-direct.com/gallan/

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#1060220 - 01/08/08 12:56 PM Re: 10w40 in the jeep 4.0? [Re: Gary Allan]
wavinwayne Offline


Registered: 01/06/05
Posts: 7519
Loc: North Alabama
 Originally Posted By: Gary Allan
...You won't find 0w-10 oils anywhere...


But they ARE available, if you are persistent enough. Mostly racing-specific oils, though.
_________________________
Silence is golden, but duct tape is silver.

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