The market for both new and used Class 8 trucks is tight, but those with the desire to upgrade equipment or start a trucking business of their own are still finding some trucks to buy. At some point, however, the market will change, just as it always does. Trucks will be easier to find and cheaper to buy.
Whether you plan to buy a new or used truck, the engine remains one of the most important items to consider.
In years past, diesel engines for many trucks were produced by one of three manufacturers — Caterpillar, Cummins or Detroit Diesel. A few truck manufacturers produced in-house engine models, but often offered a choice of engines that included one of the big three makers.
Then Daimler purchased Detroit Diesel and incorporated its offerings into the Freightliner and Western Star truck brands. Caterpillar phased out manufacture of truck engines to focus on its heavy equipment sector. Cummins engines remain an option for some buyers, but all of the major truck builders now supply their own engine brands.
For years, the 15-liter engine ruled the sales lots. The addition of electronics produced more power than ever, even when diesel fuels were changed to remove sulfur and new emissions standards were introduced. Smaller engines worked for local routes and lighter-duty work, but buyers wanted the 15-liter engines for power and longevity.
The choice today is typically between smaller engines. PACCAR offerings Kenworth and Peterbilt, for example, may come standard with a 12.9-liter MX-13 engine. A smaller version, the 10.8-liter MX-11, is an available option on Class 8 models.
Years ago, an 11-liter diesel engine would have been considered laughably small for a Class 8 truck. The PACCAR version, however, offers up to 455 horsepower and 1,700 lb.-ft of torque — enough to get the job done.
International still offers the 15-liter Cummins X15 but also has its own 12.4 Liter A26 engine that produces up to 515 HP and 1,850 lb.-ft of torque.
Freightliner offers a variety of displacements in its Detroit-branded engines, ranging from the 12.8-liter DD13 to its 15.6-liter DD16. Also offered are Cummins X12 and X15 powerplants.
Volvo offers its D13TC (turbo compound) engine as standard on its VNL models but lists its D11 and the Cummins X15 as available
Mack Truck has similar offerings with its 11-liter MP7 and 13-liter MP8 engines.
With all of the available choices, it’s easy to generalize that smaller engines reduce fuel costs while larger engines provide more power. However, fuel economy and power are only two considerations when choosing an engine.
The intended use of the finished truck is a good place to start. Smaller engines are designed to pair with the latest automatic-shift transmissions to provide enough power for normal use. Automatic-shift transmissions are designed to keep the truck in the gear and engine RPM that provides the greatest amount of torque. Tractors that are used to pull normal loads in average conditions should have no problems, and their owners will benefit from reduced fuel consumption.
Trucks that will receive heavier use, however, may need more oomph. Drivers who frequently run mountain routes where heavy loads must be pulled up mountain grades might opt for larger displacement engines for the increased horsepower they provide. Heavy-haulers that pull over-dimensional freight will likely choose the 15-liter engine with a 13- or even 18-speed manual transmission.
Some drivers have complained that smaller engines may provide enough power but must work harder to do so, causing them to wear more quickly. Manufacturers offer warranties that should put such fears to rest.
When choosing an engine, it’s also important to consider service requirements. Recommended service intervals can differ between manufacturers, but there’s more to consider than how often to change the oil. The type of oil used is a consideration, too.
Some manufactures recommend synthetic or synthetic blend oils that can add to an engine’s maintenance cost. Some require the use of modern variants of engine oil.
For many years, oils have been assigned classifications by the American Petroleum Institute (API). Starting in 1985, engine oils classified CE, CF and CG were formulated to meet higher demands for high-temperature deposits, oxidation resistance and soot accumulation. Later, classifications CH-4, CI-4, CJ-4 and the latest, CK-4, were developed to be compatible with new emissions systems required by the government.
One thing all these oils had in common was “backward compatibility.” That means each new oil still met the requirements of the one before. So, if an engine was built to require oil classified CH-4, it was still safe to use the newer CJ-4.
That’s not true of the latest oil classification of AF-4. This new oil type is designed to work with greenhouse gas emissions equipment, and even to work with exhaust treatment systems that haven’t been introduced yet. It’s the oil of the future, but it can’t be used in engines that require oil classified CK-4.
It’s extremely important that truck owners understand which type of oil is required for the engine in each truck and doesn’t mix them. Oil in the AF-4 classification may still be hard to find at some truck stops, so it might be best to carry an extra gallon along in case it’s needed.
Engines also differ in the number of filters required during maintenance, and the cost of replacing those filters can vary. It’s always a good idea to know what filters are needed and to carry spares, just in case. While it may never be necessary to change an oil filter on the road, having one in the storage compartment can help prevent multiple stops in search of a maintenance facility that has the right filter.
Choosing the right engine is an important step when investing in a new or used truck. Knowing the available options can go a long way toward having the power needed to get the job done while controlling the cost of operation to maximize profits.
Cliff Abbott is an experienced commercial vehicle driver and owner-operator who still holds a CDL in his home state of Alabama. In nearly 40 years in trucking, he’s been an instructor and trainer and has managed safety and recruiting operations for several carriers. Having never lost his love of the road, Cliff has written a book and hundreds of songs and has been writing for The Trucker for more than a decade.