You may know that Cummins diesel engines have no decent competition when it comes to towing. That's why many RVs were built using these reliable and powerful engines. Cummins offered basically two wonderful options - the 5.9-liter and the 6.7-liter engines. These units were both wonderful in terms of specs and reliability. But what about their towing abilities?
Today we'll look at some specs of these engines and will have a thorough look at the towing capacity features. We'll tell you which engine you should choose for your project or when looking for a used RV for your family vacations.
Let's dive in!
5.9-liter Cummins diesel
This 24-valve engine had numerous variants with its horsepower ranging from 235 to 325 hp. But the main thing is its torque (469 to 610 lb-ft) that is available at 1600 RPM. This was specially made to ensure wonderful towing capacity.
The engine was produced in several generations and was used on numerous cars and vehicles. Its relatively high gas mileage and wonderful longevity ensured the popularity of the unit. Actually, the estimated life expectancy of a 5.9 Cummins diesel engine is around 350 000 miles. Then you can easily repair it by installing new piston rings and valve parts and then drive another 100 000 miles.
The towing capacity of the engine is not specified by the producer as the unit was installed on many types of vehicles with different gross weight numbers. So, we suppose that 20 000 pounds will be the limit of towing weight for this engine. But we know examples when people successfully towed 30 000-pound trailers and had no issues with the engine.
6.7-liter Cummins diesel
The 6.7-liter unit was a much later version of the engine that was mainly used in Dodge and RAM trucks. This diesel engine was very good unless you compare it with the older motors like the 5.9 engine we've been just talking about. The lifespan was much shorter - we would say 250 000 miles is the top mileage you can get out of this engine.
But it had good things, too. The power of 370 hp, the immense torque of 850 lb-ft, huge payload, and wonderful towing capacity are the main advantages. For towing, you can get around 22 000 pounds max if you use a RAM truck or a Dodge vehicle. If it's an RV or something heavier than a truck, the towing capacity will be a little lower.
But if you tow more than recommended using this engine, it can be broken soon. So, better stick to the manufacturer's recommendations.
5.9 vs 6.7 engines
If we had a choice, we would go for the 5.9 engine. Yes, it has lower torque and less power, but it can tow physically one and a half times more weight than the newer 6.7-liter engine. Cummins started introducing additional emission-reducing technologies with its new 6.7-liter diesel engine. And unfortunately, this shortened the lifespan of the unit.
Also, we would agree that towing your trailer in the city is better with the 5.9 diesel engine coupled with manual transmission. The 6.7-liter engine that came with automatic transmission was much better on the highway because it had more power and torque to get the weight going well.
But in the end, it doesn't matter much which engine you choose. They are both made to tow weight and they are both quite reliable and long-lasting.
About the authors
The CarAraC research team is composed of seasoned auto mechanics and automotive industry professionals, including individuals with advanced degrees and certifications in their field. Our team members boast prestigious credentials, reflecting their extensive knowledge and skills. These qualifications include: IMI: Institute of the Motor Industry, ASE-Certified Master Automobile Technicians; Coventry University, Graduate of MA in Automotive Journalism; Politecnico di Torino, Italy, MS Automotive Engineering; Ss. Cyril and Methodius University in Skopje, Mechanical University in Skopje; TOC Automotive College; DHA Suffa University, Department of Mechanical Engineering
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