Base 4.3L V6 is underwhelming for a work truck.

A mere 195 hp and 260 lb.-ft. of torque is on offer from the asthmatic engine.

Entry-level 4.8L V8 makes much better 302 hp.

Power is up, but there's a big price to pay at the pump.

4.8L is the second-least efficient engine on offer.

Fuel economy reaches up to 19 mpg highway.

Like the Silverado it shares a platform with, the Sierra offers two 5.3L V8s.

Both V8 engines produce 315 hp and 335 lb.-ft. of torque.

At up to 22 mpg highway, the V8 is the most efficient non-hybrid engine.

All-aluminum 6.2L V8 is the most powerful engine, towing over 10k lbs.

Its 403 hp can get it from 0-60 mph in 5.8 seconds.

2013 Sierra Hybrid pairs 6.0L V8 with two electric motors driving the wheels.

Power is rated at 332 hp and 367 lb.-ft. of torque.

Impressive fuel economy comes through at up to 23 mpg on the highway.

Whether it's an iron-block or aluminum-block, the 5.3 has great gas mileage.

Plus, it offers many fuel-saving features and the best driving performance.