We ended up renting a small SUV, a Chrysler Pacifica, when we were in California. The rental place claimed to be entirely out of anything smaller (it was 2am, so it’s plausible). The rental place said it got 26 mpg highway, so we chose it over the Chrysler 300 which was smaller but only got 24. But we did some highway driving between Santa Barabara and LA, and the best we did was 16. That said, it was pretty fun to drive. You could actually, like, accelerate, and go up hills.