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Buses with Detroit DD5 and DD8 Engines Have Fewer Regens, Improved Fuel Efficiency

HIGH POINT, N.C.  – School districts with Thomas Built buses equipped with Detroit DD5 and DD8 engines are now documenting conclusive evidence of immense reductions in parked regens and improved engine efficiency, proving these engines truly are in a class all their own.

School buses equipped with the new Detroit DD5 and DD8 engines have been running throughout the country for more than two years and their performance is proof of the enduring value offered by clean diesel-equipped Thomas Built Bus models. Based on a sample of 2,300 buses across the U.S. and Canada with DD5 and DD8 engines, around 70 percent of school buses equipped with the new Detroit engines experienced zero to two manual regens in their first 8,000 miles. Most impressively, a select number of buses have accumulated more than 50,000 miles and had zero parked regens to date. On average, the buses equipped with the two engines have returned an average of 9.45 miles per gallon in fuel economy.

“When we debuted the Detroit DD5 and DD8 engines, we had solid research on how well the engines performed in trucks and in a testing environment. While we knew they would perform well in school buses, I think it’s fair to say that we underestimated just how well these engines would perform,” said Jed Routh, vice president of sales, services and marketing for Thomas Built Buses. “With the reports that are coming in, districts are saving significantly on fuel economy and are seeing a dramatic reduction in parked regens – a ten times reduction in regens, in fact, than what we typically see in older diesel engines. As more and more districts convert to DD5 and DD8 engines, we hope to continue to hear these transformational stories and start to shift the perception of today’s new diesel school bus.”

The Detroit DD8 engine is a 7.7L inline 6-cylinder medium-duty engine specifically developed for the Thomas Built Buses Saf-T-Liner HDX. It boasts a horsepower range of 260-300HP and a torque range of 660-860 lb.-ft. The DD5 engine is a 5.1L inline 4-cylinder engine adapted specifically for the Thomas Built Buses Saf-T-Liner C2. It offers a 200-240 horsepower range and a torque range of 560-660 lb.-ft.

In addition to improved fuel economy and regens, these new Detroit engines are easier than ever to maintain, with some of the longest service intervals in their class, and their fuel efficiency is the best in the industry, saving schools and fleet owners money on fuel and lowering their total cost of ownership.

Since the introduction of the DD5 and DD8 engines in mid-2018, Thomas Built Buses has delivered nearly 7,500 new C2 buses equipped with the state-of-the-art Detroit DD5 and DD8 engines.

For more information on the DD5 or DD8 engines, customers should contact their local Thomas Built dealer.

About Thomas Built Buses:

Founded in 1916, Thomas Built Buses is a leading manufacturer of school buses in North America. Since the first Thomas Built bus rolled off the assembly line, the company has been committed to delivering the smartest and most innovative buses in North America. Thomas Built Buses, Inc., headquartered in High Point, N.C., is a subsidiary of Daimler Trucks North America LLC, the largest heavy-duty truck manufacturer in North America and a leading manufacturer of class 4-8 vehicles. Daimler Trucks North America produces and markets commercial vehicles under the Freightliner, Western Star and Thomas Built Buses nameplates. Daimler Trucks North America is a Daimler company. Learn more at


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