Is this the same research and engineering staff second to none which gave us wiring insulation that crumbles to nothing?... for three models years?

For all the years I've been reading this board and others, this is the first I've heard of the caveats you’ve mentioned.

I don’t just follow sexy advertisement. Please realize that I am a bearing metallurgist who works very closely with a lube specialist for a major bearing company. Our company has also been around 100 years. My colleague (STLE member) and I have seen all kinds of bearing and lube problems, in industry and on this board, but none of the abovementioned situations. I suppose you’ve seen more damaged bearings than I have, and correctly attributed their cause of failure?

I don’t see how races and seals - especially very tight MB races - can loosen by using grease other than the manufacturer’s grease. I don’t know how you base this statement... experience from a single event? Most bearing failures after service are from improper or abusive installation methods, often from improper seating, which causes clearances to open up during use. Nobody in our company has ever complained of a lube being too slippery. The reason other greases aren’t specified is usually because the manufacturers simply don’t feel it’s worth the time, money, and effort to have their greases qualified by for approval by a car maker. Just because a product isn’t on somebody’s approved product list doesn’t mean it won’t function satisfactorily.

Why hasn’t Pennzoil passed on their warning beyond their lube stations? They don’t seem to mind the DIYer buy and use their synthetic gear lube wherever they please with no warning and let them ruin their cars. Why hasn't this information been passed on from MB to the DIYers? There are a lot of people on this board that want to do what's best for their vehicles and may possibly be harming their vehicles.

It’s not just the oils and sulfurs that provide a protective coating on gears, but the zinc compounds, which are present in synthetic lubes. MB would be hard pressed to prove someone used synthetic in the differential to deny warranty unless the owner told them so. Again, nobody has been reporting widespread degradation of their units from using modern lubes. Otherwise there’d already be a long line of people crying at the local dealers.

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95 E320 Cabriolet, 169K