Chevrolet (GMC), Ford and Ram each offer a diesel engine option in versions of their light trucks. All manufacturers claim superiority over the others from different perspectives: maximum horsepower, maximum torque, best in-class horsepower, best in-class torque, 0 – 60 acceleration times, 1/4 mile times, fuel economy, and on. Each of the three diesels are excellent engines, well-engineered, reliable, powerful, and a significant improvement upon their somewhat less impressive predecessors. Let’s take a look at each of these engines individually and then we’ll share with you, based on our research, our choice of the best light truck diesel engine available.
General Motors 6.6L Duramax LML
In 1998, General Motors and Isuzu (which has for years designed and manufactured diesel engines for truck, marine, generator, and other industrial applications) joined forces to develop the first high-pressure common-rail, direct-injection diesel engine in the United States. This engine, the aluminum-headed 6.6L Duramax V-8 hit the market in 2001 with a very impressive 300 horsepower and 520 lb-ft of torque, a vast improvement over GM’s unimpressive line of Detroit Diesel engines that preceded it.
The current version of the Duramax, known as the LML, produces 397 horsepower and 765 lb-ft of torque. Upgrades to the latest specification include the use of super-fast-reacting piezo-controlled injectors (which are capable of multiple injections per cycle for optimal combustion), along with a B20 rating, allowing owners to use fuel blends with up to 20 percent biodiesel without voiding their warranty or risking damage to the engine or fuel system.
The Duramax LML 6.6 liter V-8 engine is rated at 397 horsepower (296 kW) at 3,000 rpm and 765 lb·ft (1,037 N·m) of torque at 1,600 rpm.
Cummins B-Series High-Output 6.7L
In 1989, as has almost been the case, Dodge had considerably fewer resources to develop an in-house diesel engine. Instead of an expensive, and risky, internal investment, why not purchase from an outside supplier? And what could be a better choice than Cummins B Series engines? After all, Cummins’ reputation as a manufacturer of diesel engines stretched back to 1933, and that a Cummins diesel engine qualified on the pole for the 1952 Indy 500. Instant credibility and sales increases for Dodge.
When launched, the long stroke inline six cylinder B-Series was rated at 160 horsepower and 400 lb.-ft. of peak torque, more than the V-8 rivals from GM (246 ft. lbs.) or Ford (345 ft. lbs.) but less than half the numbers for today’s High-Output 6.7-liter Cummins turbo diesel.
The 6.7-liter Cummins Turbo Diesel I-6 is available in three versions for Ram trucks. The lowest-powered is paired with Ram’s six-speed manual transmission, which delivers 350 horsepower at 2,800 rpm and 660 lb.-ft. of torque at 1,400 rpm. The second option matches the Cummins to the Chrysler six-speed automatic for 370 horsepower at 2,800 rpm with 800 lb.-ft. of torque at 1,600 rpm. Third, the Cummins 6.7L High-Output Turbo Diesel is paired with the relatively new, very slick Aisin six-speed automatic transmission, pushing out 385 horsepower at 2,800 rpm, the most powerful Cummins generates best-in-class torque of 865 lb.-ft. at 1,700 rpm
The Cummins 6.7L High-Output Turbo Diesel is rated at 385 horsepower (287 kW) at 2,800 rpm and 865 lb·ft (1,173 N·m) of torque at 1,700 rpm.
Ford “Scorpion” Power Stroke 6.7L
Like Dodge, Ford initially purchased and co-developed diesel engines with the company known to most as either International Harvester or Navistar (depending upon the year). The partnership begin in 1983 with a 170 horsepower, 315 ft-lb 6.9L V-8 and ended with a 6.4L, that while a good performer, offered terrible fuel mileage. What really damaged the relationship and drove Ford to an in-house solution was the 6.0L engine which was so problematic several hundred trucks required engine replacement.
The all-new Power Stroke V-8 engine, developed alongside AVL, an outside engineering firm, made its debut in 2011 models. The upgraded 2015 6.7L Power Stroke engine produces 440 horsepower and 860 lb.-ft. of standard torque, an increase over the earlier version. Changes include a larger turbocharger with larger compressor vanes, high-pressure common-rail fuel injection system that delivers up to five injections per combustion cycle for optimum throttle response and fuel efficiency, and full B20 capability.
The Power Stroke 6.7L V-8 Turbo Diesel is rated at 440 horsepower (328 kW) at 2,800 rpm and 860 lb·ft (1,166 N·m) of torque at 1,600 rpm.
And the winner is …
The Power Stroke mounted in an F-450 chassis provides the same ongoing tractive capacity as this diesel-electric Electro-Motive E7 locomotive
This is the 6-cylinder version of the RT-Flex96C. Imagine another 8 cylinders added to its length!
The Wärtsilä RT-flex96C is a two-stroke low-speed diesel engine designed for use in large container ships. The largest 14-cylinder version is 44 feet high, 87 feet long, weighs over 4.5 million pounds. The massive diesel generates 107,390 horsepower and 5,608,310 ft-lbs of torque (at 104 rpm!). With a 38 inch bore and an 8.2 foot stroke, a full grown man could easily hide in one of the cylinders. Now THIS is truly the king of the diesels!