2008 Pontiac G8 GT

While the G8 GT is built in Australia, its 6.0-liter pushrod V-8 is a sibling of the engine that appears in several full-size General Motors pickups and SUVs. It features an aluminum alloy block and heads to reduce front weight, which helps handling. Peak torque is a huge 385 pound-feet, which occurs at a relatively low 4,400 rpm. True dual exhausts end with four tips.


To raise highway fuel economy to 24 miles per gallon, the engine’s computer deactivates four cylinders at cruising speed. In our test vehicle, there was a barely noticeable hiccup when the engine went from V-8 to V-4 operation at moderate speeds. The engine is mated to a version of the six-speed automatic that appears in the Corvette.

Engines and Mileage

The G8 GT has a high rear-end gear—2.92:1—to enhance fuel mileage. However, a super-low first gear—4.03:1—allows it to produce that impressive acceleration.


For most drivers, the base G8’s V-6 will offer more than enough power. The dual overhead cam 3.6-liter makes an impressive 256 horsepower, thanks partially to variable valve timing. Even more significant: The V-6’s large torque peak of 248 foot-pounds occurs at a low 2100 rpm. G8 GT drivers will need good reaction times to beat a G8 V-6 in a stoplight-to-spotlight competition. The V-6 gets only slightly better fuel mileage: 17/25 to the V-8’s 15/24.


As part of the extensive effort to keep weight under two tons, while retaining BMW-like 50/50 weight distribution, the G8 GT’s battery is located in the trunk and an electric air compressor replaces a spare tire.