One interesting thing I read was that synthetic oil was actually invented by the Germans in WWII to respond to the Allied interruption of petroleum supply lines. So its been around a while, with API supposedly approving it in the '60s for use in automobile engines. I use it primarily because 3.5k oil changes are a pain in the ass. One can stretch an oil change interval with synthetic out to 7.5-10k and come out cheaper than using dino at 3.5k even though good dino would be half the price. Given the superior lubrication and the fact that you don't have to mess with it until 10k later it's seems a no-brainer. If you have seals that are borderline you will cause leakage though.

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'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)