You get screwed one way or another. It is just luck. The 10 minute place that I go to for my oil change is a patient of mine. I take care of him, he takes care of my car. Either way, I always watch and only get oil change. I don't even bother with vacuum, tires, or anything else. Oil and filter. That's it. I got a complimentary car wash at the car dealership once and they scratched the wood trim with the abrasive vacuum hose (car was only a couple hundred miles old). Worse, they backed the car out with the door open and bent the door backwards (1000 mile car). Oh, they also rotated my asymetrical staggered IS350 wheels. You get messed up service at the dealer and you get messed up service at the cheap places. I just came back from NTB - the new kid (was being trained at the time) couldn't remove the tire off my rim if his life depended on it. Fortunately, somehow, they didn't break off the TPMS or scratch the rim - but he didn't lube the tire well enough so they had to WAY overpressure it to seat the bead - I'm surprised the tire didn't explode. Sometimes I suspect the MB dealer my father goes just breaks things on purpose so he needs more work. My father went for a battery change on his S500, they change batt but forget to reset some stuff. Navi doesn't work suddenly and now they want 3500 to fix navi. Oh, better yet - they change the display because the speedo stopped working and they accidentally add another 0 to the odometer so now it says 1/2 million miles instead of 50K miles and all sorts of CEL and service lights are on now.
This kind of crap happens everywhere though. Do you think when you go in for surgery, there is no scam? My wife is a RN and she says there is a doctor that she used to work with that was part of a small group that worked together to scam patients. One doctor would do all the work - the other one or two would literally come in and say hello, and leave and the patient and insurance would get a bill for three doctors. The patients are old cold - what do they know? They scratched each others' backs.
All this boils down to ethics and living life honestly and truthfully. Hopefully, you will be lucky and won't be scammed too much in your life.