Some personal experience w/ mechanics here.

I once hit a rabbit, and it got sucked up inside my car somehow and cracked the radiator. Took it to Jack Williams, they quoted me over $5,000, gave me a detailed list of everything that would need to be fixed and why. The car was barely worth a grand so I said fuck it, got a new car, and gave the broke down one to my FIL to let him do whatever he wanted with it. My FIL looked at it, did nothing but replace the radiator (cost him a couple hundred dollars), and it’s been driven ever since (3+ years now) with no issues.

Got my new car after that, and was having an issue with my rear wheel making a scraping sound. Took it to Pep Boys, and they told me I need to replace both rear brakes, rotors, AND calipers, which was going to cost me a shit ton of money. I took it back to the dealer to tell them and they looked at it and fixed it...and whatever it was wasn’t even related to the brakes.

I’ve found a mechanic I trust since then.

My biggest pet peeve about mechanics at these chain places though is that they all seem like. such. douchebags. It must be part of the upsell process. Like when I took my car in for the radiator, the mechanic at Jack Williams treated me like an idiot when I was shocked at how much it would cost, and acted like he couldn’t believe I had the nerve to ask him if everything he said needed to be done was necessary (which none of it besides replacing the radiator was). And he was even more shocked when I said “screw that I’ll just drive it home” instead of putting over 5 grand into a thousand dollar car. Same with the Pep Boys people.

My guess is they try to act like people should know all these little things (even though no one does) to make them feel embarrassed and try to discourage them from asking questions and trying to save money. Then if you tell them you do need to take a day to think about it they try to make you feel like an idiot (they know you nothing about cars, you know you know nothing about cars) to pressure you into leaving your car with them then and there so you will be on the hook for any repairs they want to do to your car.

I’m sure that approach works on a lot of people but me personally I’d enter my car in a destruction derby before I’d give a single cent to someone who is an asshole for a car repair.