Newer diesels are tuned totally different and may only need five minutes warm up in cold weather.
Our Cat takes a few minutes , the colder the longer, to get it rolling.
They talk about cylinder wash down if let idle too long.
We use cruise control to idle about100 rpm and for at least five minutes usually ten if cold especially. During that time power cord is disconnect as well as sewer and water, Awning in jacks up and pads stored. Sometimes takes 15 minutes.
We are usually in no rush so we don't start out at 0 dark thirty.
We try to ensure our neighbors are up and about usually gone when we prepare to leave.
We have tried to leave with the engine and transmission stone cold. It doesn't want to go anywhere.