Since about 2000, Detroit and Prevost have been at work trying to reduce the exhaust emissions from Big Green:



Unfortunately, the result has been that the 475hp of the engine has been reduced to about 400hp at the wheels. And on an H3-45, for example, heat dissipation requirements have also increased and so has mileage.

The fix is to re-set the injectors to 75 and open up the pump outlet restricter for increased power and economy. This will result in about .7 mpg increase and some more power.

The future is a tad more grim: Within the next 18 months, Prevost shells will be fitted with a roof-type exhaust a la Blue Bird, as exhaust temp will reach 650F due to emissions requirements (good for melting asphalt, bad to stand near).

After that is the new Volvo 12.7 engine with the stack, to be made in Hagerstown, PA, the old Mack plant, which Volvo owns.

The good news is that if you have a pre-2000 coach, you don't have to worry about any of this, just have fun with what you have, as those days are gonzo!