I had a tire go bad in 4,000 miles, due to a massive alignment issue.

You just have to look at them.

Last time I went to Jiffy lube I had them back down super fast by just asking that very question: "show me."

They said I needed to flush my transmission (car had 100k miles). Transmission was new, still under warranty due to a replacement. I told them "Show me the fluid on the dipstick. If it's dirty, I want your assessment in writing so I can get it replaced under warranty."

I made the manager walk to my car, pop the hood, wipe off perfectly clean transmission fluid, throw his guy under the bus "It was my tech that told me", I promptly asked for the key to my car and told them I was never going back.