I am printing out the SAE paper to read as I type this. My '86 with 295k has had semi-synthetic (Lubri-Moly) or, more recently, fully synthetic Amsoil for the last 120k miles. Changed every 18k miles now, actually every six months (I drive about 36k annually), with the filter being changed at three month intervals.
Having studied the synthetics quite a bit, I will probably never go back to fossil-based lubricants in anything. My brand new Kubota diesel did not come home from the dealer until they put in the Amsoil products I took them. It will outlast my MBs because I hardly use it!
At our new house we are putting up a refurbished wind generator. We live in the boonies (and love it, btw) and the wind blows a lot in Nebraska. They man I purchased it from and who is installing it puts a brand new warranty on them, UNLESS you add something to the gear lubricant. The only turbines to ever burn out that he put in have had something added to the lubricant - including but not limited to Slick 50. The only lubricant he uses is Amsoil. The important part is not the brand, but the fact that it is synthetic, so therefore cannot and will not burn up. He changes this lubricant once a year, btw.
I know this is not a car engine, the it is similiar in that the turbine turn very rapidly, but, naturally, there is not a problem with pollution from hyrdrocarbon fuels.
Who has experience with Redline synthetics? I just started using their Diesel Fuel Catalyst, which seems to help my car run smoother.