According to the U.S. Department of Energy, diesel engines offer 30- to 35-percent greater fuel economy than comparable gasoline engines. Diesel fuel also has higher energy density than gasoline, which means less fuel is required to generate the same power as gas, improving overall fuel economy.

The recently updated RAM 3500 is the current towing capacity leader. With the truck's 6.7-liter Cummins diesel engine and the right drivetrain, Chrysler says the RAM 3500 can tow a whopping 30,000 pounds. That's well ahead of rivals such as the F-350 Super Duty, and the Silverado and Sierra 3500 HD.

Rock Auto has parts for heavy trucks, tractors, snowmobiles, boats or motorcycles. You can buy it online by using the "Part Number Search" tab if you know the part number. Rock Auto also list lights, belts, hoses, and other parts in our "Tools and  Universal Parts" tab by size.