IIHS Top Safety Pick. Delivers 29 Highway MPG and 20 City MPG! This GMC Terrain boasts a Gas/Ethanol I4 2.4L/145 engine powering this Automatic transmission. WHEELS. 4 - 18 X 7.0 (45.7 CM X 17.8 CM) DENALI-SPECIFIC. TRANSMISSION. 6-SPEED AUTOMATIC (STD). TIRES. P235/55R18... via V12 Software