I can see why you'd make that assumption, but in fact you're wrong on both counts. Prowl's in-car behaviour is somewhat disgusting -- he has been known to dunk his burger in his milkshake while driving -- but he's a fastidious soul and vain to boot, so he clears out all wrappers and napkins when he disembarks.
The Dratchets, on the other hand, own at least three dogs at any given time, and Ratchet's Volvo station wagon, a.k.a The Brick, is their designated transport. The upholstery is basically dog hair, with an assortment of muddy towels in the back for wet dogs, windows besmirched by the imprints of dog noses, and a pervasive odour of dog and cigarettes throughout. (His car being one of the few places he still is allowed to smoke.) So shocking is the inside of this car that Drift forbids him to give anyone a ride in it, and sends one of his outrageously modified Toyotas, parachute at the back and exhaust pipes spitting fire, as the designated conveyance whenever someone needs a lift to the airport.