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Message: [QUOTE="TARM, post: 370154, member: 578"] Maddiesel, That is correct to a point. But this has mostly to do with the spread of the cold and hot vis. Both oils have + s they are a bit different. I do not think you can go wrong with either. The base oil is superior in the 9000. The additive packages of either is IMO better than any other oil out there other than possibly some boutique oils. The fact is you can not look at what other engine find as good even diesels as these HPOP injection systems create a very unique situation on the effects dealing with oil. POA handles fuel and coolant and moisture dilution best. The group III handle other things better. I tend to find 5w40over 15w40 to offer better throttle response especially when the oil is not up to normal operating temp. It should also offer better start up protection as well. That is where a significant amount wear comes from as I understand it. The fact is UOA is one of the best ways to know what oil is working best for your setup and driving habits. It can be different. I do not think you can go wrong with either of their oils but one may offer advantages over another depending on setup and use. Its possible that MAY benefit you. There is one thing I have noticed in the trend with most top quality oils and our HUEI system. The oils seem to break down to a SAE 30 and then they slow way down. Some will get there sooner than others but they all seem to hit the wall once they get to 30W. Now I have not had the chance to try this. I have wondered if the tolerances of our engines tend to work well in the 30w range. This is in the shearing effect only. To test only this and not a oil for best over all use I have wanted to try a straight 30SAE oil. This way there are very few if any viscosity modifiers as its not a multi-vis oil. I want to see how much it actually shears. . It seems to me that the ones running good quality 10w30 have always reported very good UOA and shearing was less as well IIRC. 10w30 use the be the oil of choice with the earlier 7.3s and even back to the 6.9 days. They have also reported what I have seen going from 15w40 to 5w40 with throttle response. If these had been full syn used I wonder if it would have been that much better. I am trying to find what ever I can as far as UOA in power strokes over on BITOG with 10w30. If for anything just to fill my curiousity. Honestly IMO get a top quality oil in the 5-15w/30-40 range will work well. I find Schaeffers offers that as good or better than other oils and at a good price point to boot. [/QUOTE]