Safer, Cleaner Diesel: The Growing Trend Of Diesel Buses

The reputation of diesel has come a long way.

While some people still picture clouds of thick, dark smoke, the reality is diesel has improved by leaps and bounds in a short amount of time. Since becoming standard in 2010, the ultra-low sulfur formula of today’s clean-diesel is doing more for our planet by putting less into the environment each year:

  • 2.6 million fewer tons of nitrogen oxide

  • 110,000 fewer tons of soot and particulate matter

The benefits don’t end with improvements over old diesel. When compared to alternatives like propane and gasoline, clean-diesel emits six times less carbon monoxide and 645 times less non-methane hydrocarbon.

Clean-diesel buses, such as the Saf-T-Liner® C2, are making a real-world impact. As published in School Transportation News, manufacturer Thomas Built Buses now has multiple years worth of data to compare its clean-diesel fleet against traditional diesel buses.

What have been the biggest areas of improvement? Mileage and regen.

TBB 12407 Diesel Emissions Graphic c7 7


With tight school budgets across the country, improving diesel bus mileage is a top concern. The good news is those numbers are improving.

According to Jed Routh, former vice president of sales, services and marketing for Thomas Built Buses, most clean-diesel fleets are averaging 9.45 miles per gallon. This is an increase of one to three miles compared to older diesel buses. Improvements are also being seen with special-needs buses, which tend to idle more often. These buses are averaging roughly 8.3 miles per gallon.

In total, the data suggests overall fuel economy improvements of about 10-15%. With more and more clean-diesel vehicles hitting the road, the benefits will keep compounding.


The time-consuming process of a manual regen can sideline a bus for 30 minutes or more. It’s an unfortunate, daily reality for many older diesel vehicles. Due to the stop-and-go nature of buses, temperatures do not get hot enough to burn off the residue.

However, that’s changing.

New clean-diesel buses are fixing the issue automatically. The residue is being removed while the bus is in service. In fact, according to Routh, more than 70% of the thousands of tracked buses have a total of two parked regens or fewer. This enhanced reliability can make entire fleets more efficient

Technology keeps pushing forward. With continued innovation, the buses millions of kids rely on each day can be better for both schools and the environment

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