CHELSEA, Mich. – I had the chance to ride in a DD15-equipped Freightliner Cascadia at Daimler Group’s Chelsea, Mich. proving grounds. The powerplant lived up to its advanced billing as a quiet engine on the oval.

As promised, the DD15 is in fact much quieter than the Series 60.

The Cascadia is a quiet truck to begin with; coupled with the DD15 it was easy to forget we were driving a diesel.

I was able to converse with fellow passengers in a normal voice and the sound of rubber on road and wind on metal was more audible than the engine itself.

Gone are the knocks and rattles that were often associated with the Series 60.

We also tested the engine on some major hills – up and down grades ranging from 9 to 15%. The engine brake, much like the engine itself, was extremely quiet. And it had no problem holding us back on the 15% decline.

The three-stage engine brake is an updated version of the famous “Jake” brake and has been fully integrated into the engine.

The company says maximum braking performance in the DD15 is 500 hp.

We’d never encourage braking the law (or by-laws for that matter), but you’d be unlikely to get a ticket for using the DD15’s engine brake in residential areas.

The improved torque response was immediately evident while launching from a standstill. And the engine’s broad torque band was also apparent.

This engine pulls right down to 900 RPM and engineers suggest lowering shift points from what you’re accustomed to with current engines.

The broader torque band also means fewer downshifts are required. The performance enhancements over the Series 60 are real.

If the DD15 delivers on its promise of improved fuel efficiency, than it appears Detroit Diesel will have a worthy successor to its Series 60 on its hands.