Most of the big news lately surrounding GM's full-size trucks has been centered around the half-ton models of the Silverado and Sierra, but the 2014 HD models are getting minor updates ahead of their expected comprehensive overhaul in 2015. The most significant news, after a nearly year-long wait since the initial announcement, is the availability of the bi-fuel CNG models of the Silverado and Sierra 2500 HD.

The CNG models get a specially prepped variation of GM's fourth-generation Vortec 6000 V-8 with hardened valves and valve seats giving it bi-fuel capability. Dubbed the LC8, the engine produces the same 360 hp and 380 lb-ft of torque as the gasoline-only L96 engine when running on gasoline, and 301 hp and 333 lb-ft of torque when running on CNG.

Silverado HD models equipped with the gasoline engine also get a standard 4.10 axle ratio for 2014 for improved acceleration and an improved standard towing capacity of 13,000 lb. The 3.73 axle ratio is still available for buyers looking for optimized highway fuel economy. Finally, a factory-applied sprayed-on bed liner is available for 2014, an option also offered for the first time on the 2014 1500-series trucks. Nissan was the first to offer a factory-applied bed coating on the 2004 Titan, with Ford following suit in 2009 on the Super Duty, and Ram in mid-2010.

Source: General Motors