Oil wt question for 08 Jeep Grand Cherokee 3.6

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I recently purchased an 08 Jeep Grand Cherokee and the manual calls for 5/20wt oil. I then read an article from a lubrication firm stating that these low weights were recommended because the manufacturers needed them to meet CAFE mileage standards. It also said this was done to the detriment of the engines which would do better on 5/30w. I believe I am out of warranty at 60K and was considering switching to the higher weight at the next oil change and would appreciate any thoughts on this oil weight situation.
 
Originally Posted By: JackB1
I recently purchased an 08 Jeep Grand Cherokee and the manual calls for 5/20wt oil. I then read an article from a lubrication firm stating that these low weights were recommended because the manufacturers needed them to meet CAFE mileage standards. It also said this was done to the detriment of the engines which would do better on 5/30w.

Out of curiosity, what lubrication firm stated this? Did they have specific examples of "detriment" and this applied to your engine? One would think the OEM would have tested the specified oil fully in all conditions and thus they would be in a better position to make recommendations versus a lubrication firm.
 
Try a thin 5w30 like Valvoline WB, or Mobil Super once you're out of warranty and see what you think. A single OCI isn't going to hurt anything. First a UOA on 5w20 would be uesful so you could later do one on the 5w30 and have something to compare it to. I doubt you'd see much difference.
 
The 2008 Jeep Grand Cherokee came with any of the following engines:

3.7L V-6
4.7L V-8
5.7L V-8
6.1L V-8
3.0L V-6 CRD

I suspect JackB1's Jeep has the 3.7L. The only Jeep with the 3.8L V-6 was the Wrangler.

The new Pentastar 3.6L V-6 calls for 5W-30 as I recall.
 
I was hoping that someone would provide an opinion of the information shown on the lubrication site I listed above. I would prefer to switch to 5/30 not only for the reasons mentioned in the report but also because my local BJs, which has the best prices, only carries 5/20 in one brand. Shell I think.
 
Originally Posted By: JackB1
I was hoping that someone would provide an opinion of the information shown on the lubrication site I listed above. I would prefer to switch to 5/30 not only for the reasons mentioned in the report but also because my local BJs, which has the best prices, only carries 5/20 in one brand. Shell I think.


That's a pretty dated article but it still had a lot of pertinent information. My suggestion would still be the same, try a thinnish 5w30 and decide for yourself what you think.
 
OK, Valvoline is mentioned above as a "thinnish" oil as well as Mobil Super [what is that?]. I also need a reminder of just why some 5/30s are considered "thinnish". On the surface it does not seem to make sense and if some are actually a little thinner is it really enough to make any difference. Ican get Mobil 1 5/30 and Shell at a good price. What could happen if they are used. My gut says nothing but I am willing to listen to something that has some scientific evidence to back it up.
 
This article is very dated, modern 5w-20 API GF-5 oils will protect very well. I believe that it is advisable to use the oil speced by the engineers ,they do know something about the engines they designed and built. What this article does not address is the cold flow and start up protection advantages that 5w-30 and 5w-20 have compared to 10w-30,10w-40 oils.
 
Originally Posted By: Thax
This article is very dated, modern 5w-20 API GF-5 oils will protect very well. I believe that it is advisable to use the oil speced by the engineers ,they do know something about the engines they designed and built. What this article does not address is the cold flow and start up protection advantages that 5w-30 and 5w-20 have compared to 10w-30,10w-40 oils.

I used to call on engineers and I agree that they know best. The problem is that often marketing departments trump engineers when it comes to the bottom line. I can understand the concept of using 5/20w to meet CAFE standards [if true] at the risk of slightly less engine life. It could be a compromise that both departments could live with but something we owners may not want to.
 
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Valvoline told me the HTHSv for the VWB 5w30 was 2.9, which is why I referred to it as a thinner 5w30, the actual cst@100 for it is 11 which is higher than many others, it has a pretty high VI.
 
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