I seen you guys talking about idling the other night and Jeff talking about washing the cylinders down.
I've had a few pre 2002 Dodge cummins trucks, the aftermarket compines make a high idle kit that is plug and play. Bumps the idle up, to 1200 or 1500 rpm, makes it easier on the engine for long periods of idling.
I was always to cheap to buy one, bought this adjustable stick at some truck stop, slid it under the lip of the dash, other end on the pedal, bump the idle to 1250 or so, made it warmer to sleep in the truck over night, mine never generated heat idling, but if the idle was bumped to 1250 or so it would put out heat.