Excessive idling can actually damage your engine components, including cylinders, piston rings, and crankshaft bearings. A diesel engine creates combustion of the injected fuel by the heat of compression. An idling engine is not operating at its peak temperature which means that all the fuel is not completely combusted when injected. This leaves fuel residue that can collect on cylinder walls where they can contaminate and cause fuel oil dilution of the lube oil, decreasing it's viscosity. It's a good idea to add diesel fuel cold-weather treatment or an anti-gel additive to ensure that you maintain the low temperature flow characteristics of the fuel. Ensure your glow plugs are working properly and install a block heater for good cold weather starts.
My background..... Retired USN Chief Engineman ..shipboard diesel main propulsion, ....civilian job, fleet manager