Some of these four-cylinder cars are exclusively internal ... And for that extra money, they sprint to 60 mph just a few tenths of a second faster – 4.2 and 4.1, respectively.

they sprint to 60 mph just a few tenths of a second faster -- 4.2 and 4.1, respectively. It's no 5.0L, but the Mustang four-cylinder EcoBoost engine is certainly enough power for most rental car ...