Not that maintenance in general is a scam, but that places that do it are. He used long time ago to do its own maintenance. TBH he really doesn't take care of his cars, which is weird, my grand mother keeps her cars super pristine. Her honda element hits the dealership every 6 months most of the times with less than a 1000 miles difference.

I really don't know what my granpa thinks but he thinks they try to oversell stuff and charge too much for things he could get in autozone for cheaper and do it self. Stuff like that sort, but yeah, he doesn't take care of his cars just tires, breaks and stuff that breaks.