Yup, that's right.....

"Maybe BMW want their cars to wear-out sooner rather than later. I'd would think BMW's use synthetic oil/grease etc. and most likely silicone brake fluid. You can bet they treat all the exposed rubber with silicone."

While I seriously doubt BMW is trying to make their cars wear out fast (based on their free service, long guarantee and history if nothing else....) they do in fact use synthetic oils and grease. Hydrocarbon lubes, not silicone. Just man made mineral oil, more pure than what you'd dig up.

True also that Si based brake fluid is used, no doubt 'Armor All' or simialr on the exposed rubber as well, but then neither of them are lubricants, right? They also use leather on the seats.....

Use what you want of course, and you don't have to take my word for it, but Si based products are a very bad choice for high load steel on steel lubricants. As others have said. Especially if hydrocarbons are already there (a 'oil and water' thing.....makes a big mess).

BTW the silica is far far from 'microscopic ball bearings', it's amorphious (no crystal structure, highly irregular). Flue ash. Huge surface area (which is why it improves concrete so much). It's a *thickener*, not really what you'd want to use as a lubricant if you had a choice. Think "sand".......

Doug Owen