What's The Difference Between Cummins B, L, And X Engines?

Cummins is a world-renowned builder of diesel engines, having developed diesel-powered pickup trucks and semi-trucks for decades now. In order to cater for such a wide range of vehicles, Cummins manufactures a variety of different engines, which are categorized by which series they belong to. Among the most popular diesel engines built by Cummins are the B, L, and X Series of engines.

The main difference between these three different series of engines is in their size. The smallest of all three is the B Series, a family of engines which consists of four- and six-cylinder variants. The capacities of these engines range from 3.9-liter in the four-cylinder variation, to 5.9-liter for the larger inline-six models. Peak power arrives in the larger inline-six models, which can deliver up to 210 horsepower, alongside 516 lb-ft of torque. Stepping up from this, Cummins offers the L Series diesel engine. Here, the main difference from the B Series is that all L Series engines are 8.9-liter inline-six engines, sporting up to 430 horsepower and 1,361 lb-ft of torque.

Finally, we end up at the X Series. With this 14.9-liter inline-six engine, Cummins provides up to 675 horsepower and 2,050 lb-ft of torque, dwarfing the other two by a considerable amount. The main reason why these engines vary so much in size and output is due to their intended purpose — another key difference between all three.

Starting with the most powerful, the X Series, Cummins designs engines such as these for heavy-duty use, fire and emergency vehicles, for example. The X15 is Cummins' flagship engine within the X Series, and the type of vehicles powered by Cummins X15 engines are often semi trucks – you won't find this huge inline-six under the hood of even the biggest Ram pickup. On the other hand, the B Series family of Cummins engines does have an interesting link with the all-American pickup truck brand. Dodge started using Cummins engines in 1989, and the first engine supplied was the 5.9-liter B Series lump. 

These differences highlight Cummins' approach of tailoring each engine series to a specific role. The X Series serves heavy-duty applications, while the L Series is designed for medium-duty vehicles, such as school and transit buses. By contrast, the B Series was always intended for production pickup trucks.