08/07/2026
If you run diesel coaches, you know the DEF derate headache. A sensor faults and the coach limps to the shoulder with a full load aboard.
Metro Magazine reported this month that the EPA has proposed removing those emissions-related engine derates on new heavy-duty diesels. Instead of dropping into limp mode when a DEF system faults, the bus would keep running and alert the driver so the fix happens safely. The American Bus Association backed it, and the EPA is taking comment on extending similar relief to coaches already in service.
Here is why it lands for used buyers. On any modern diesel coach, the emissions system is one of the first things to check, and derate history tells you how a unit was run and maintained. A more forgiving rule makes the whole diesel fleet, new and used, more dependable on the road. Reliability is most of what you are actually buying.
Worth a read for anyone running or shopping a diesel coach. Have DEF derates bitten you out on a route? Curious how often it happens.
The EPA is proposing to remove DEF-related engine derates for new heavy-duty diesel vehicles, a change bus operators say would improve safety and reliability while sparking debate over the future of...