This question is not about a Mercedes, but I figured you guys might be able to help. I have a friend with a cherry 1968 Chevy Camaro Z/28 who put about 2.5 gallons of diesel fuel into the gas tank. The advise he was given at the time (not from me) was to fill the tank the rest of the way with the proper fuel and "run it out". Well, that was two or three full tanks of gas ago, and the car still gives off excessively smoky exhaust. Is the continuing smoke due to residual diesel in the fuel tank/lines that will "run out" over time or will have to removed (i.e., clean or replace the gas tank and/or fuel lines), or has more lasting damage been done to the engine?