Yesterday I took my car for an oil change, once it was done I realized that they had'nt topped up the oil completely.. so I opened the cap, poured in half a quart.. then forgot to put the cap back :(
15 miles later, I realized that smoke was coming out of the hood. So I pulled over and looked...
You'd be better off buying a low mileage standard car. A lot of people make the mistake of thinking that bmw, mercedes... are perfect cars. They end up crying like hell.