Class 7 vs. Class 8 Truck Engines: Which One is Right for You?
If you’re entering or expanding your operations within the long-haul or delivery industries, you’ll likely need more trucks, a commercial driver’s license (or a driver with a CDL), and a well-vetted business plan.
While all of these elements are important, the vehicle is going to be the center axis that everything else in your business revolves around—so a lot of consideration should go into the purchase of your next truck.
As an owner or operator, you should understand the differences between Class 7 trucks versus Class 8 trucks, and more specifically, what the difference in their engines can mean for your company.
Truck Sizes
Class designations are generally based on the Gross Vehicle Weight Rating (GVWR), which is the maximum safe operating weight of a vehicle. This weight is established by the manufacture of each truck line, based on their engineering specifications. Therefore, the Gross Vehicle Weight (GVW), which is the scale-measured weight of your vehicle and everything inside it at any given time, should always be lower than the GVWR.
To establish your payload capacity, subtract the curb weight from the GVWR to calculate exactly how much you can safely haul. When adding a trailer to the scenario, you’ll also need to know what the Gross Combined Weight Rating (GCWR) is, which accounts for the combined weight of your vehicle, plus the weight of the trailer itself and all the cargo within.
With this in mind, a Class 7 vehicle is usually defined by a GVWR of 26,001 to 33,000 pounds. They are typically powered by 6.7-liter to 9-liter medium- to heavy-duty diesel engines and are built for regional stop-and-go use. A Class 8 truck offers a GVWR of 33,001 pounds or more, with 11-liter to 16-liter engines that are designed for sustained highway driving and hauling heavier loads.
Under the Hood
As you might expect, Class 8 engines are much larger than Class 7 engines, providing them with the displacement they need to generate between 1,500 and 2,000 pounds-feet of torque, which is ideal for pulling heavy loads. Class 7 engines generally produce between 800 and 1,000 pounds-feet of torque, which is still powerful enough for flatbed trailers and box trucks, as well as municipal buses and even medium-duty dump trucks.
Despite the power difference, Class 8 engines are built for the long haul while Class 7 engines are more suitable for shorter driving distances with more frequent stops along the way. Considered among the best high-mileage engines, Class 8 engines are built for B50 design lives of a million miles or more, which indicates the statistical average lifespan of the equipment. It is the time or operational usage at which 50% of a tested product population is expected to fail, degrade, or fall below a specified performance level.
In other words, while a B50 design life of 1,000,000 miles means half of the Class 8 trucks on the road will need to be overhauled before reaching the million-mile milestone, the other half will still run strong. The typical B50 design life for a Class 7 truck engine usually ranges somewhere between 400,000 to 700,000 miles.
Two Sides to Every Story
There are other considerations to take into account when deciding between a Class 7 vehicle and a Class 8 truck. For example, if you have a limited start-up budget, Class 7s are about 20% to 25% less expensive to purchase. Their smaller dimensions and tighter turning radiuses make them better suited for navigating tight city streets and congested traffic. Also, they are often exempt from some bridge laws and routing mandates that affect the bigger rigs.
As for the Class 8s, they can safely haul much bigger loads and offer a 50% to 70% longer total service life when maintained properly—even though the upfront purchase price and maintenance costs can be higher. Their larger-displacement engines and heavy-duty cooling systems give them the ability to haul heavy loads over extended periods of time without overheating or breaking down, even with extreme elevation changes where thinner air can deprive a vehicle’s engine of full oxygen consumption capacity.
Meet Your Match
No matter the size of the engine, we have the largest online inventory of new and used vehicles so you can find the exact truck you need. While new trucks represent top value, keep in mind that a used vehicle is a great option when you need to keep an eye on your cash flow but still want a quality piece of equipment.
Barrett Baker