WASHINGTON, D.C. – Model Year 2011 and newer diesel engines powered more than 1/3 of the trucks on American roads last year, and as many as 2/3 of the vehicles in selected states, the Diesel Technology Forum reports.

Engines of that vintage accounted for 30% of vehicles in 2016 and 25.7% in 2015.

Indiana, Tennessee and the District of Columbia had the highest percentage of new-generation Class 8 diesel trucks, accounting for a respective 66%, 60%, and 48% share.

“About 21% of all commercial trucks (Class 3-8) use gasoline and about 4% use other fuels, with those using natural gas amounting to less than 1%,” added Allen Schaeffer, executive director of the Diesel Technology Forum. “Especially for the largest of trucks, no other fuel matches what the newest generation of diesel technology continues to improve upon: efficient performance, low-emissions, reliability, durability, low-cost operation, and maximum flexibility in utilization, routing and fueling.”

The group released the numbers while stressing the environmental gains that are realized through late-model engine technology.

“The more than 4.9 million new-technology diesel trucks now on the road have removed more than 26 million tonnes of nitrogen oxides (NOx) and 59 million tonnes of carbon dioxide (CO2) from the air. On average, truckers saved $2,600 in fuel, which adds up to 138 million barrels of crude oil – that’s 50% of the entire U.S. Strategic Petroleum Reserve, saved by just a few thousand trucks,” Schaeffer said.

Fleet Advantage’s latest Truck Lifecycle Data Index says the newest Class 8 diesel trucks can save up to US $26,600 in annual fuel costs compared to a 2012 model.