For nearly twenty years we have been engaged in testing light duty diesels for their emissions for the state. Being at altitude (5000 feet) we began testing before the advent of sensors to tell the computer what our altitude is. We test for the density of the smoke emitted from the tailpipe under a full load at 60, 50, and 40 miles per hour. These are the times a diesel will smoke its worst if it is going to smoke at all. With the return of gas emissions testing this year we are still doing the testing in private stations, not at the state contractor. So, yes we are still testing diesels and the Air Care Colorado does the gas testing. Please feel free to call us at 970-482-3971 if you have any questions about emissions testing and we will be happy to help.