KBB.com 10 Coolest Cars Under $25,000. Only 81,503 Miles! Scores 30 Highway MPG and 21 City MPG! This Ford Mustang boasts a Intercooled Turbo Premium Unleaded I-4 2.3 L/140 engine powering this Automatic transmission. ENGINE: 2.3L ECOBOOST (STD), Whe...