It is a joke. I have seen it on a dozen form pages, but with a differnt kind of car each time but The EXACT story

 

Diesel, i lean torwards your option, i do think it's a joke. But i'm pretty sure there are enough stupid ppl around to try those things out (so the appearance of that kind of stories wouldn't be so strange). I once was told by a "mechanic" that you could clean the engine by letting it run for a short while using diesel in place of the oil...

 

does he know that u dont just change the oil b/c its dirty but b/c it loses it viscosity as well so it not lubricating the engine as well as new oil...