[hexspeed]

Checking mileage by DDEC? (Sorry if I got that wrong)

DDEC = Detroit Diesel Electronic Control System (engine computer)
At a high level, in addition to managing the operation of the engine, DDEC tracks and stores a lot of info useful for diagnostics and fleet management. One of the the tracked parameters is mileage. The DDEC module has a diagnostic port that mechanics can use to read / download all of the stored info.  Some owners invest in the interface module and laptop software that allows them to read stored info and display key DDEC parameters in real time (revs, speed, temps, pressures, miles, engine hours, etc., etc.).

Personally, I’m a conservative enough buyer that getting the coach to a shop that can read and analyze everything on the DDEC would be a required part of my pre-purchase inspection. The experienced gurus may have other views on the value of this.