alternative to 5w/40 without full-syn.?

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In regards to the "oil seeping" issue, my thoughts are as follows:

Since its no different than a dino oil in terms of the base oil, no it should not cause any leaks to leak anymore than they already do.

Now for the big HOWEVER:

Since it is a Diesel oil with extra detergency and dispersants to deal with diesel soot, it may very well remove some of the "gunk" that is plugging some of your leaks today. Thus tomorrow, it may leak more.

Tough call in that regards. On my '88 Jeep Cherokee, I have actually watched the one leak I did have not leak at all since switching to Rotella T 5w40. What does it mean? Tough to say, but I am happy with it to date.
 
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Originally posted by MNgopher:
The Rotella T Syn 5w40 is a group III base oil product marketed as a synthetic. I will grant that Shell uses a different procss to generate this Group III than other Group III producers. In any event, under what is considered a "true" synthetic on this board, it is NOT a synthetic or blend, but a good group III oil. I wouldn;t consider it to be different than a dino oil in that repsect.

Well, the Rotella 5w-40 is getting pigeonholed according to the rather strict definitions of Group III and IV.

Group IV is PAO only, and Group V is esters, etc... while Group III is basically unconventional base oils from refined petroleum oil.

The Rotella-T is neither- it's a synthetic oil produced from a wax base.(XHVI base stock) In other words, Shell takes slack wax from refining and converts it into base stock. It's just as "synthetic" as PAO oil, insofar as it didn't start with refined oil to begin with. The only meaningful difference between it's process and the PAO process is that one starts with a wax solid, while the other starts with gas. Neither improve on Group I oils, which is what most Group III oils do.

I'd say that the XHVI base stock probably ought to have its own III+ or IV- category to separate it from the rest of the group III oils- it's not the same thing.
 
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Originally posted by TSoA:
Rotella is no run-of-the-mill GIII oil. Although GIII it is not hydrocracked, it's derived from Shell's own slack-wax process. A wax isomerate supposedly equal to PAO. The final blended product is chock-full of Shell's own additives too.

GIII's what processes to the oil companies use to make them? Can they be hydrocracked or is the process against the property of the GIII ?
 
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Originally posted by Robbie Alexander:
GIII's what processes to the oil companies use to make them? Can they be hydrocracked or is the process against the property of the GIII ?

The way I understand it, here's how the basestock groups are produced:

Group I: Solvent-refined.

Group II: Solvent-refined, then hydrocracked

Group II+: Solvent-refined, then hydrocracked to a greater degree than Group II

Group III(most of them): solvent-refined, then multiple stages of hydrocracking to make a very high viscosity index base oil. Still a very similar process to the Group II/II+ process, just more of it.

Group IV: polyalphaolefins- molecules created by polymerizing ethylene gas.

Group V(esters, and everything else): Various procedures
 
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