I ordered an auto code-reader. I didn't realize they were so cheap now. When I checked a few years ago, they cost hundred of dollars, so I didn't buy one.
A local auto parts store used to read codes for free, but they stopped. Since I like to do any repairs I can do on my own, this will come in handy. The service engine light is on in our old car, so I should have this device on Friday and will be able to determine what's what.
Like most people, I stopped doing oil changes myself decades ago, because I don't want to go to the trouble of transporting old oil for disposal and because oil changes are so cheap now, you can't save much money doing them yourself. You can still save a lot of money on other simple repairs going the DIY route.
The latest: the master power-window switch control in the center console was all but cooked. I bought a used master control on ebay in like-new condition for $49. Literally, it took less than 5 minutes to remove and replace the control. All I needed was a slim screwdriver to slip out the old one, unplugged two harnesses and plugged them into the new control. Popped the whole thing back into the console, and that's it. Net savings versus dealer quote: $278.00. We'll take it.