Most of the subcategories have fluffy articles. The “Under the hood” series covers various parts of the car and is the most practical, in my opinion.

I know you don’t want to research a specific model, but I learned more about cars by subscribing to a forum for my specific car. I’d browse random articles about maintaining or modifying my car. In doing so, I’d find out about general car theory and I found extra motivation to learn things that I could do to my car to save on maintenance or improve fuel economy.