Ashton Kutcher is so disgusted by people who keep their sports utility vehicles (SUV) clean, he recently sprayed Ja Rule's Land Rover with fake sewage.

Kutcher believes anybody who drives the large vehicles should use them for the rugged activities they're built for.

He says, "If you're gonna drive an SUV, you gotta get it dirty and if you're not gonna get it dirty I'm gonna get it dirty for you!

"These vehicles were specifically made for outdoor activities. You need to be taking these vehicles off-roading and getting them dirty. Cleanliness does not earn points in sports utility vehicles."

To support his viewpoint, Kutcher ruined Ja Rule's night out with a group of pals by having workmen spray the rapper's vehicle with fake raw sewage on his prank show PUNK'D.

During the episode, which aired in the US last night (07AUG05), Kutcher was also the cause of Ryan Cabrera's car troubles, when a Porsche the singer had borrowed from on-off girlfriend Ashlee Simpson's dad Joe was singled out as the reason a crane had dropped an air-conditioning unit on a parked car.

Cabrera admits, "I almost peed down my f**king pants!"