Volvo says its newest trucks will put fewer harmful pollutants into the air than the Internationals being made by Navistar.

It’s the latest in the ongoing battle between the big truck companies over whose emission-reduction system is the best.

Navistar went with an exhaust gas recirculation or EGR system that’s designed to burn up harmful gases in the engine. Its competitors – including Volvo, Daimler and Paccar – went with selective catalytic reduction or SCR technology, which treats the gases in the exhaust system by adding urea.

Navistar recently urged federal and state officials to re-examine SCR, charging that truck owners could skip adding the urea and the truck would still run just as well.