Cold combustion does cause some blow by, and if it's done a lot will quickly contaminate even the cleanest, freshest oil, causing it to become super black and very gritty, which surely would damage the engine. I have heard that the Cummins likes to run at 1,800 rpm. That is the Goldilocks zone for it. The shop foreman at the dealership suggested that if I am doing only a lot of local, around town driving at reduced speeds, to gear down to increase the rpm. Also, if you're only making a couple few short stops I think it's far better to idle rather than shut it down, BUT the goal is to reach operating temperature as soon as possible. So, if you have the "idle up" feature with the cruise control buttons, idle up when you make your stop/s. One might even increase the rpms further by continuing to tap the resume button after engaging idle up. I believe--but I may be wrong--it is only the low idle speeds that will cause too cool combustion. No one can drive off with your truck with the key fob in your pocket.
Was it in the Diesel Supplement that I read engaging full exhaust brake will increase the coolant temperature more quickly? This might be another way to get that operating temperature up there quickly, to help keep the oil cleaner.
