> I don't see much similarity between '80's Chevrolets and late model BMWs as far as engine technology goes.

When it cones to wear and things oil impacts, I see a lot. Has BMW gone away from plain bearings? Are tolerances and clearances bigger or smaller in newer engines? Are newer engines more or less susceptible to oil viscosity changes?

Newer engines are more demanding of oil than older engines. The justification for longer oil change intervals has much more to do with engine oil changes than with engine design changes.

While I must admit I am not an "engine man," I also have a Mechanical Engineering degree and a bit of a mechanic background.

So you may be quite correct, but since I do my own oil changes, I personally prefer to err of the conservative side and not go for the extended oil change intervals. As a former Product Planner for Ford, I do remember being in a couple of meetings between marketing and the engineering people arguing about service intervals, with the Marketing people pushing hard to extend the intervals, to get a sales advantage, and the engineers arguing against extending them. It was more like an adversarial negotiation than discussion of facts.

I imagine even BMW internally has similar "meetings."