My father actually used to work at an oil change. Yesterday he told me that they typically blow out the air filters and that doing this sometimes allows for trash to get into a certain part of the engine. (I can't remember what it's called). Apparently their boss told them to do it even though it was bad for the car. Said boss owns an oil change, mechanic shop, and an inspection/tire service, as well as a car wash. So yeah, he used to make all of his employees do shady shit to force them into using his other services more or less. 

Moral of the story: Don't blow out your air filter. Change the bitch. 
____________

Also, none of that includes a fact about me, so here's one: While they leave good tips, old drunk guys that come in and look me up and down like a piece of fresh meat make me feel icky.