H4 engines, also known as boxers or flat-fours, may not be as common as inline-fours or V6s, but they still pop up in a lot of modern cars.

With a reputation for rugged reliability, Subaru's all-wheel-drive lineup offers cargo space and capability, with plenty of models on the used market.

In the 1990s, Subaru experimented with new ideas, one of which was to twin-charge a flat-four engine for extra power. Here's how it went.