FuelConsumption (adjusted for speed) ie, mpg @ 100 mph != mpg @ 50 mph.
Cargo (in cubic whatever is appropriate for you)
Cars have a LOT of options. This will change things quite dramatically when all things are considered. FWIW, I was a master mechanic before I became an engineer, and factory trained by Volvo, Fiat, Lancia, Subaru, Toyota, Jeep, Chrysler ... and have the paperwork to prove it.