I've had mechanics tell me my cabin filter is bad on a vehicle that didn't have one.
I've had mechanics show me how gross my spark plugs were in a diesel engine sedan.
I've had mechanics tell me I need new tires on a truck I had just replaced the tires on two weeks beforehand, and driven in mud.
I know more about my truck's issues than the guy who just did an oil change and casually glanced at a couple other things.
All that said, I still appreciate an actual mechanic (not the lube guy who started on Tuesday) telling me what they found wrong. You ever know when you might actually miss something.
Those are shit mechanics who are just trying to steal as much money as they can. I would avoid them and call them out whenever possible. I've had some good mechanics who go out of their way to save you time and some who have actually helped without charging extra. Not to say it's required but the stigma of bad mechanics has ended up being the way it is by having people oblivious to what happens under their car's hood.
Yeah, I don't go back to places like that, I leave reviews, and I tell anyone who mentions car trouble "don't go to this place here"
There's a shop about 35 minutes from me I've been at for awhile now, they've saved me quite a bit of money over the years and the ONLY time I've had an issue with something, THEY contacted ME to ask me to come back in so they could fix a mistake.
I had a diesel mechanic tell me that the diesel engine in my school bus needed new glow plugs. This was at least a more reasonable scam as diesels normally do have glow plugs, I just happened to know that my engine (a DT466e) doesn't have them.
To be fair, I've told someone spark plugs on a diesel after I changed a few on gas cars.
They have glow plugs. I knew what I was saying, but it was a long day.
They go in the boom holes and help with said booms. Don't look at me because I'm not an English major. When I order parts I point to the catalog and grunt like a caveman, because my brain is smarter than my mouth.
I own a school bus with a diesel engine and one mechanic I went to told me I needed new glow plugs. Unfortunately for him I was aware that my particular diesel engine doesn't have them.