In view of the continual rise in gas prices we are looking at buying an older 5 or 6 clyinder turbo diesel Mercedes-Benz wagon. I have access to used cooking oil and am thinking about making bio diesel. Anyone here have any actual experience with these old MB's? What are the pros/cons of 5 cylinder versus the 6 cy engines? Anything about these oldies to be especially wary of? I have a good shop, some tools, and although I don't like to, I can wrench a little. All opinions or experiences appreciated.