Actually the synthetics are well established as providing superior protection throughout all viscosity ranges.

Actually the synthetics are well established as providing superior protection throughout all viscosity ranges. The reason for the persistent mythology around seal shrink is that in early years the group 3 and group 4 base Oils for synthetics lacked the high wax content that kept seals in great condition. Those same waxes crystallize and gel the oil at cold temps where the synthetics are far superior. The adition of diesters in synthetic oils has long since taken care of that problem. Diesters break down with water however so a coolent leak on a synthetic oil run vehicle can amplify problems and may be why some of the "seal breakdown" legend persist.
Since few of us revev this northern -Alberta driverwill run our baby at below -10 the need for synthetic oil is a tough sell. The additive package in a high quality group 2 or 3 base oil becomes more critical than the synthetic vs mineral argument. Keep in mind a synthetic oil is simply a severely "hydro cracked" base oil -a man made oil because it does not exist in nature.There are some specialty oils that replicate original design spec additive oils but they are not a typical shelf item at least not in Canada. At least one local has destroyed an engine. Running an API SN product supreme 20W50 they have too little anti wear additive for the older 911's. One product recommended but our lube tech dept and it is a competitor so I took the reco seriously, was Penrite. Always check against OEM reps though. At day's end we should be aware that the great advances in lube oil development were occurring as our cars rolled off the production lines the last 30 -40 yearsn . This is likelythe reason for such diverse opinion and confusion on the topic, By the way that was not the Swepco Supreme that Pelican sells a great choice btw rather it was a generic shelf brand in Canada, sorry for the mis spelled words - week 2 with an iPad,

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This post was auto-generated based upon a question asked on our tech article page here: Pelican Technical Article: Changing Engine Oil - 911 (1965-89) - 930 Turbo (1975-89)

[Nick at Pelican Parts]

Thanks for the info.

- Nick

[dshepp806]

I'm not so worried about "seal shrink", but, moreso, the provided Z & P levels in the selected oil. I'm stating this as an owner of a '89, flat tappet engine.

You made no mention of Z&P levels. Do you consider this particular as important?

Best

Doyle