A common must-have for many folks in a heavy duty (or now light duty) truck is a diesel engine. Diesel engines are best known for their ground-breaking torque, smooth delivery, and longevity. Diesel engines have been around for decades and now with modern technology, they leave the factory with impressive numbers and specs. All Class 3 diesel trucks can now tow far more than 30,000 lbs and haul over 5,000 pounds of payload, exceeding most customers demands. In this article, we will be ranking some of the best diesel engines ever made for American heavy duty trucks.
  1. 5.9 12 Valve Cummins 1989-1998 : Released for the 1989 model year, the 12 Valve Cummins is the diesel engine that helped generate the movement for modern diesel engines. It was the first heavy duty truck to feature a turbocharger for better performance along with a Bosch P7100 and an intercooler down the line to not only maximize performance but reliability. An inline 6 was considered (and still is considered) engineering greatness due to fewer complications, lighter design, and one set of cams. The 5.9 Cummins is best known for its reliability, but the earlier models have the best reputation due to less emissions equipment and a “simpler” design. First generation Dodge Cummins trucks are very hard to find which is what makes it so special. However, transmission issues plagued the Cummins but if you want the ultimate diesel engine, a manual Cummins from this era is the way to go.
  2. 7.3 Power Stroke 1994-2003: The second best diesel engine is also the biggest in terms of displacement, the 7.3 Power Stroke developed by Navistar is considered by many a legend. Impressive power, towing capabilities, and fuel economy (considering the engine size) are all attributed to the 7.3 Power Stroke. No major problems ever plagued the 7.3 other than cases of the engine overheating and sensors (such as the cam position sensor) going bad. If the turbocharged version came before 1989, then the 7.3 may earn the top spot but due to the fact it was last American heavy duty truck to feature a turbocharger, the 7.3 comes in second.
  3. 2006-2007 LBZ Duramax: Only available for two model years, the LBZ Duramax was arguably the most reliable and most powerful diesel engine offered during this time. The 6.6 Duramax with the Allison Transmission was indestructible and GM had developed an engine that made its buyer happy with current prices of the LBZ Duramax in mint condition approaching $35,000 with low miles. The Allison transmission was superior to the 48re transmission that was offered in 24 Valve 5.9 Cummins and the 6.6 Duramax was far more reliable, stronger and significantly more powerful than the 6.0 Power Stroke. Unfortunately, due to strict emissions, the LBZ was replaced by the LMM Duramax.
  4. 2007-? 6.7 Cummins: For the 2019 model year, Cummins unveiled its new engine that featured an outstanding 400 HP and 1000 lb. ft. of torque for its HO model in the Ram 3500. The 6.7, introduced for the 2007 model year, featured new emissions equipment and higher power ratings that made it a competitor to the LBZ Duramax. The 6.7 engine is still used today and has had versions that give buyers a choice to what suits them best. The transmission issues seemed to have been solved in 2013 with the introduction of the new Aisin automatic transmission. Up until 2019, Cummins was the last diesel engine manufacturer to feature a manual transmission, however, buyers should not be disappointed with the new specs that have been released.
  5. 2011-? 6.7 Power Stroke: The first diesel engine built by Ford on their new platform had those questioning the reliability of the all-new yet advanced power plant. Navistar had let down a lot of Ford Super Duty buyers particularly with the 6.0 and 6.4 Power Stroke. However, the 6.7 has proven to be a great engine delivering impressive power and fuel economy results but some argue it was far too late since Cummins and Duramax had better reputations at the time. The 6.7 currently leads the segment in horsepower at 450 HP and class 4 towing. It seems as though Ford has found a reliable yet powerful engine after almost a decade of poor reliability with the 6.0 and 6.4 Power Strokes.

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