In October 2004 I took delivery of a new Peterbilt 379 127" BOC, 248" wheelbase, 70" sleeper, all the options available. The first Cat C-15 with Acert emissions and two turbos delivered in our area. I read all the manuals on the new engine. Had an 18 speed transmission and the max HP then, 550. This was by the way my 4th computer engined truck and I read all those manuals too.
Cat recommended no warmup, no idle down unless working very hard. The three minute idle rule was legislated by states and towns to stop noise. Has not a thing to do with the engine. Once oil pressure is up go to 1000-1200 rpm for warm up if ambient temps are under 32 degrees F.
We truckers would high idle our trucks when stopped for heat or A/C. Its rough sleeping in the truck when its not comfortable. If you stop for fuel its not efficient to shut the truck off when your going to leave immediately after. In the winter frequently the truck would run for the whole trip, sometimes up to 6 weeks. You will never go to that extreme in your motorhome so why all the discussion? If I was rich I could have purchased and installed an auxiliary engine and generator but they cost so much and add weight which lowers your pay. Your motorhome has one so you can shut the big engine off and keep warm or cool and charge the batteries.
So I find this discussion a pure matter of common sense and personal preference.
