I once worked with a guy who thought he could do anything. He decided to flush out the cooling system of his wife's car with one of those "T" connectors. He cut into the air conditioning hose and proceeded to flush the condensor. He didn't realize what he had done until the next spring when his wife said the air conditioner didn't work and he took it to the mechanic.

Another guy I worked with who was a chemcial engineer tried to change his oil at the engine bay at the plant. He drained the oil and replaced the plug. He filed it with 5 quarts of oil. The engine didn't have any oil but the transmission sure did.