Check your oil
Inside your engine, dead dinosaurs (or synthetic dead dinosaurs) get pushed around by modern machinery. The sloppy mix called oil makes sure none of the carefully crafted pieces of metal grind against each other and keeps efficiency much higher than would otherwise be possible. While dinosaur fossils tell us about the time the dinosaurs were alive, used motor oil tells us about the time it spent inside the engine.
Blackstone Labs can definitively test your oil and tell you exactly what’s wearing, how fast, and whether or not your engine actually needs the “standard” 3,000-mile prescription of an oil change. You’ll only get a report since the last oil change, but it’s an inexpensive way to learn a lot about how your car has been driving for that time. Their standard oil analysis only costs $22.50 (as of this writing) and will tell you all the bare essentials you could want to know.
All you have to do is collect some of your old oil (bear in mind, this can be transmission, differential, or engine oil) in a sealed glass container at your next oil change and send it in to them. While I haven’t tried this myself, I’m intrigued as to the results. Have you had your oil analyzed before, and was it actually a useful endeavor?