Diesel engines don’t warm up at “normal” idle speed—they must be run at a “fast idle” to generate heat. Check with your dealer or the manual for how to access your fast idle speed. Many coaches use the following technique: As soon as you start the cold engine, engage your cruise control (press the ON/OFF button) and then touch the “RESUME” or “SET” button (could be either one depending on your manufacturer). Your engine should remain at the fast idle rpm. (Some rigs may have a dash switch marked “IDLE INC/DEC” to activate high idle.) This is an excellent time to finalize the last-minute details just before pulling out of the campsite. Don’t idle too long as engines manufactured after 2008 are designed NOT to be idled (emissions controls). So about one minute is ample idle time before you drive away.