MaxiVan, Sprinter, Next?

From : mark sparge

Q: hello everyone i drive an 06 ram 2500 with cummins diesel motor. it doesnt seem to hold heat very well. i can have the truck all warmed up right at the centerpoint of the temp gauge. then ill park it and shut it off. in about an hour ill come back to start it up and the temperature gauge reads stone cold and ill need to warm it up completely again. my truck seems to cool down rather quickly. i think the thermostat is ok. someone told me this is because diesel motors run on the principle of using as little fuel as possible thus a diesel just doesnt run as hot as a gasoline motor. any comments suggestions thanks in advance. the rocket man .