Today I learned things about automobiles.
Specifically, I learned the following:
The Redwood City branch office of the California Department of Motor Vehicles is much less crowded than the San Jose office. The wait to pay my car registration fees today was about 15 minutes, compared to my usual average of more than two hours in San Jose.
When someone at the DMV makes a mistake and files someone else's "Release of Title" form (as one files when one sells a vehicle) against your vehicle, you will no longer get mailed renewal notices for it. However, apparently you have no way of knowing this, aside from the absence of renewal notices, unless someone at the DMV notices this form in your file and asks you if you have any idea why it's there.
I need to remember that there's good reason to buy auto parts from the dealership rather than from auto parts stores, even though they cost more. Yes, the parts-store spark plug wires that I bought fit, but about half of them are too long.
The spark plugs and plug wires are not, in fact, the reason why my car is not running right and idling poorly, and thus the two hours that I spent today replacing them were not actually useful, and I will still need to take it to a repair shop.
Four years ago, when I was getting the smog-check-before-last for my car, I needed to replace the PCV valve (a small plastic-and-metal bit shaped and sized vaguely like an AA battery with a hose fitting on the side), and in the process of replacing it I dropped the old one beside the engine. I couldn't find it at the time, and thus forgot about it. It turns out that it landed on top of one of the spark plugs, and was still there for me to find today. On the other hand, the oil filler cap, which is screwed in rather tightly, managed to fall off last week and completely disappeared.