I got my oil changed once at a place called Speedy Lube (which is now, ironically, a Jiffy Lube) a couple of years ago in my old Pontiac. I was sitting in the waiting room and the tech comes in to show me that I need a new air filter and they would gladly charge me $25 for a new paper. I said, “No thanks” and he went back out to the car.
He finished up, I paid my $40 and left. I pull down the street to my parking lot and hear this weird whistling/tapping noise. Pull into my lot, pop the hood and find that not only had they not fasten the lid to my airbox down, but there was no freaking filter!
Went back and told the manager what the guy did, which he denied doing of course. Boy, did I have fun yelling at those guys. They gave me a new filter and a coupon for 25% off. Tore it up, dropped it on the ground and walked out.
see…now they just forget to put it back in. alot of cars would drive off and the tech standing next to me would pull the airfilter off the stand and say woops looks like i forgot to put that back in.