I am an ASE certified master tech with 15+ years experience. I completely got out of the automotive repair business because the whole industry is corrupt. Cars today (made after about 2000) are made to be maintenance free and last for hundreds of thousands of miles with minimal maintenance required. The old days of needing a tune-up every 15,000 miles is gone. So are the profits which come from a steady stream of legitimate repairs. So the industry figured out a plan: LOF due every 3,000 miles with a free inspection, then a laundry list of "preventative maintenance" items which are basically fixing things that aren't broken for the sake of profit. Mechanics at the dealer and all of the chain shops are all paid the same way: flat rate. That means for every hour billed the mechanic gets paid his hourly wage, regardless of how long he is on the clock for. Notice I didn't say "commission" because 20/20 ruined that gig.
Here's the scenario pretty much played out in every chain shop or dealership every day in every town across the country: Joe mechanic has a family to feed and has had a couple days filled with non-paying come-backs from the other mechanics or some BS warranty work that didn't pay hardly anything. Joe has been in the shop for 30 hours and has only billed 10 hours, say he makes $20 an hour his family isn't going to be happy with a $200 paycheck minus taxes, child support, and $100 to the Snap-On dealer. Today is better, he gets an oil change and free inspection to do on a car with 80,000 miles. He shops the car for all it's worth and writes himself a paycheck for 40 hours for which he only has to do about 8 hours of work. To accomplish this goal he writes up problems that overlap and the service manager charges separate labor for each operation according to the book. For example: water pump, R&R, 3.4 hours. Timing belt, R&R, 2.9 hours, Serpentine belt, R&R, .8 hours. Crankshaft seal, R&R, 3.2 hours. Camshaft seal R&R, 3.1 hours. So you see how a job that should fairly pay about 4 hours (and take a competent mechanic about 3) turns into a 12 hour labor bill. Same for tune-up items, brakes, suspension, and the worst of all are the preventative maintenance items which can be 5 or 6 hours of basically nothing. It wasn't broke before, the customer sure as hell isn't going to complain when it still isn't broke. Now can you blame the mechanic who is sent to school to find these potential problems before they turn into disaster? Or maybe the store manager who says any tech not making at least 45 hours in a 40 hour week gets *censored* canned? Or maybe the service manager who is paid a token salary plus a hefty "bonus" based on profit compared to previous months or weeks, and penalized next month's bonus if he is under this month. The mechanic is trained by the factories to ensure product sales and job security. He pops the hood for an inspection and squeezes the radiator hose. Guess where the hose will bubble up in a year or so? That's a gravy job of belts, hoses, radiator, freeze plugs, you name it whatever the customer will bear that's what he'll soak him for. It came in leaking and goes out not leaking, any money is well spent according to the customer. The mechanic did him a favor and prevented an extremely expensive head gasket failure. Next up is a fine Japanese car with nothing wrong except needing an oil change. Some recommendations and now he takes out the factory triple platinum spark plugs at 30k miles and puts in $0.49 Autolite plugs. Not bad, 2 hours tune up labor to screw in a few spark plugs. Next month he gets to do a diagnostic test on the same car for hard starting and poor gas mileage. Needs new Oxygen sensors, air filter, throttle body service, decarbonization job, valve tappet check/adjustment, and a set of platinum plugs because "the oxygen sensor ruined the old ones and the original ones". Problem is the customer forgot that the reason he needed that first tune up in the first place was due to a mechanics recommendation. The customer however, leaves happy again. His car runs good again, just as he remembers. Perfect! and $1200 for the shop in pure stolen money called profit. A no start condition results in changing the coil, module, fuel pump, crank sensor, timing belt, mass air meter, and oh yea a new ground wire to the computer which got pinched in the air cleaner box a few weeks back at the fast lube place. That tidbit gets hidden as "shop supplies".
Fixing the broken machine is what I signed up to do when I went to tech school, I learned quickly that raping customers is what the industry demands. I worked for many small shops who were honest and every single one of those places are out of business today because they couldn't keep the lights on and the place insured by fixing broken cars at a reasonable price. I worked at dealers and a couple national chains until my soul felt like it was rotting away, it's sad but the only way not to get ripped off is to personally know a mechanic who will do careful honest work on the side or do it yourself.