First it was a simple oil-cooler failure. A week later, Adam Metter noticed his ’97 Dodge Ram 3500’s 5.9L Cummins engine developed a knock, as the dualie pulled a heavy trailer over a mountain grade.

Cummins has been at the forefront of the diesel engine market for more than 100 years. At this point, an argument could be made that there are few manufacturers whose products are as well respected ...