Did you ever buy something cheap first and then upgrade later? I did that with a stud finder. Bought a $12 one that beeped at nothing, so I just gave up and knocked on walls like an idiot for two years. My wife finally got me a decent magnetic one for my birthday and it was like night and day. It sticks right to the screws and I stopped putting holes in the drywall guessing where the studs were. Now I feel dumb about all those anchors I used for stuff that weighed like two pounds.

Watched a buddy drop his transmission to fix a "rear main leak" that turned out to be a $4 drain plug gasket sweating a little. Three weekends, a rented lift, and a case of beer later, the thing still dripped until he actually looked up top. The "guy who knows cars" at every parts store is basically a fortune teller with a torque wrench.