I am looking at purchasing a 1994 850. I have a 1986 740 and am wanting to upgrade. The individual I spoke with said when they had purchased the car the garage said it was a junk engine. He states that they discovered the car had the wrong wieght oil being used, thus causing the hydrualic valves to stick open". I am quite leary as he didn't seem to know to much about the car (history) and it's features. He also stated they drained the oil and places proper oil in the engine and, after turning it over and working it in, it now runs fine....., no blue smoke in the admissions, etc. The car has only 120,000 miles and does look clean. I don't have a mechanic in his area to look the engine over (diagnostically and compression tests), so, I am having to do my own homework.

Could thicker viscosity oil cause the valves to stick?

Would such a situation cause damage?
If so, what damage would have been caused?

I know nothing about the 850's only the 740's. What other things might I look for or be aware of?

He is asking $5000 for 1994 850, 120,000 miles. Blue book says reasonable. Your thoughts?

It's a 1994 so what features (bells and whistles) would I expect to find if it checks out mechanically?

I'd appreciate any insights and comments you all could offer. Thanks!
Charlie