Compare the Buick Riviera 6.6l V8 - [1966] vs BMW 8 Series 850 CSi 5.6 V12 E31 - [1992]. Find out which car is the fastest, most powerful, lightest or has the biggest engine in our top trumps style comparison page. Find out which car has the highest top speed or is the fastest accelerating, is it the Buick Riviera 6.6l V8 or the BMW 8 Series 850 CSi 5.6 V12 E31. We'll leave it up to you to decide which is your favourite.