Which Oil is best to use for an Inline 6 engine?

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I have recently purchased a Jeep Rubicon ('05) with the 4.0L inline 6 engine.

Driving conditions...

daily commute to work 30 minutes, maybe 4 stop lights but mostly moving.

I do regular long trips of 3 hours plus 2 - 3 times a month

and

I do go out wheelin' (4x4)


The service manager for the Dealership suggested I stick with the recommended 5w-30 wieght of oil because Jeep (Chrysler) found that the heavier oils were causing premature end of life for many engines. But the service manager couldnt/wouldnt recommend a brand of oil. Any thoughts on oil filters are also welcomed.
 
He's FOS in the case of this engine. You can use just about anything (10w-30, 5w-40) and the thing will last the rest of your life. 40 weights tend to show less Fe wear in UOA. M1 T&SUV is a popular synthetic for this engine but others work well too. Even the high Fe readings probably won't shorten the life of this engine. It's very stout.


You can surely use a 10w-30 (I'd avoid 5w-30 - even the manual puts a "preferred" for the 10w-30) but I would use a 40 weight. Whether you choose dino or synth would depend on how often you intend to change it.
 
No need to go to a 40wt on a newer engine, IMHO. I'd run 5w30 in the winter and 10w30 in the summer. Either a good dino such as Pennzoil or a good synthetic such as Mobil1 should serve you well.

If you want the ultimate, try GC (Made-in-Germany Castrol Syntec 0w30), available only at AutoZone (USA).
 
I've been using M1 5W-30 in my 97' wrangler since it was new. Still runs like new, which is not very good, but it's a Jeep after all, can't expect too much from it. It uses maybe half a quart now after 84K miles per 3K miles. I'm going to try out 5W-40 next summer and see how it goes, and I'm doing the first ever UOA on it's 5W-30 this winter. Whichever has lower wear numbers is the one I'll use.
 
I used Castrol Syntec in my 2000 Nissan CrewCab 4x4 (v6), and I ran it with irregular oil changes (5-10k miles). After 86,000 miles it still ran strong and wasn't burning/using any oil.

Is the Mobile 1 better than the Castrol?

As for the AMSOil, I haven't seen that at any of the local shops.
 
Depending on your climate, if not much temps below zero F, then I would stick with a 10wXX. As for 30 weight vs 40 weight, I would look at the oil pressure. Is it in spec with 30 weight? Good. If low, may want to mix 50/50 10w30 / 10w40, or go straight 10w40. That is how I came to using 10w40 in my F150 inline six.
 
I've used 10w40 in most of my straight 6 engines but only because they were older, high mileage etc. For yours I would go with a good 5w30 in the winter and 10w30 for warmer months. If you can't decide between Dino or Synth then try a blend.
 
I do not understand why BITOG people, and the user manual for that matter, recommend 5W30 in the winter and 10W30 in the summer. What benefit do you get from using 10W30 in the summer? Aren't both oils supposed to be the same viscosity at operating temp? Isn't a thinner oil at startup always better?
 
My Jeep has 110K on it and I always used 10W30. It runs like new, uses no oil and I have never had problem, oil-related or not. My UOA earlier this years showed very good wear numbers, and at 3K miles, the TBN was still 3.1. Since you live in the PNW, you can find Chevron for a good price and a Napa Gold filter for about $6. That's all you need.
 
quote:

I do not understand why BITOG people, and the user manual for that matter, recommend 5W30 in the winter and 10W30 in the summer. What benefit do you get from using 10W30 in the summer? Aren't both oils supposed to be the same viscosity at operating temp? Isn't a thinner oil at startup always better?

Well, I won't comment in general, Winston, but in regards to this engine in particular it specifically puts a "preferred" to the 10w-30 over 5w-30. This engine, which has been unchanged for the most part, included 20w-50 at one time for relatively cool/cold temps.

Yes, they're both 30 weights at operating temps, but a 5w-30 would tend to shear more. Therefore, in instances where you may actually reach operating temp, a 20 weight or thin 30 weight may produce unfavorable results (like in the summer, maybe?). The owners manual strongly infers this. This makes the use of a 10w-30 sensible in the warmer months where no cold starting performance is needed. You're looking at it from the bottom up. This is an engine where you need to look from the other end of it ..at least in this instance.
 
Check out the UOA's on Jeep 4.0's.

IMHO Mobil-1 does not do well in this engine. You can get better #'s from regular dino oil.

So far my best #'s on my 02 TJ was with Quaker State 10w-30. Havoline also did well.
 
I've owned several inline 6 and 4 cylinder engines from AMC and Jeep with that basic design. At about 150K I have seen valve train wear on all of them, having to replace rocker arm pivots and lifters. Other than that the engines are as sensitive to punishment as an anvil. I am cheap and usually use on-sale oil, but in this case I might opt for something with a really good 4-ball wear rating like Amsoil.
 
I've ran Schaeffer's 10W-30, 15W-40 and a 50/50 mix of 10W-30 & 15W-40 in my 4.0 and 2.5L TJ's.

Highest wear 10W-30
Middle 10W-30 & 15W-40
Lowest 15W-40

The 15W-40 cut the previous wear numbers in half compared to the 10W-30. I've since decided on M1 5W-40 or Rot T 5W-40.

In your case I would run a 10W-30 till the warranty is up and then go with whatever you want from then.
 
Well, there you have it, Difranco! Clear as mud!!
grin.gif
 
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