Originally posted by RogerB:
Originally posted by Big Jim:
Originally posted by Auto-X Fil:
Aren't you happy to know you have a bad gasket, and you can get it fixed, instead of having so much sludge floating around that it plugs leaks?



That was old thinking. Current thinking is that certain synthetic base stocks tend to shrink some seals and gaskets, especially if other things are not blended in to mitigate that factor.



Actually, Jim, the "shrinking seals" thinking is from about 1972, which I think predates the sludge theory by a good 20 years, at least. Back then, there was a real problem with shrinking seals, which was quickly remedied by the oil makers. Problem solved.

You telling us it's back? What happened? Did the guys at Mobil lose the recipe? Or did the gasket-makers change everything without telling anyone?



You (RogerB) are indeed correct, the only oils nowadays that would have trouble with shrinking seals are the extremely high-end ester only (group V) oils like Motul 300V, some ELF brands, and maybe redline. To be fair though even the deposits on seal problem should be a thing of the past soon. The current crop of SM rated dino oils are so good I doubt they would ever sludge in a 3000 mile interval. For an older contour that probably saw SJ rated group II basestock oils though, sludge on the seals is a real problem (especially if maintenance was shady) and switching to Synthetic could show the problem (kind of like ripping the scab off a scrape or cut).

Ohsigmachi '96 GL MTX Zetec --I don't won't to hurt you, but it's still on my list of things to do.-- View projectSlippery Slope