Listen to Roy and Dave.
Thermal cycles are hard on any engine. Running it and not getting to full operating temperature makes it even worse.
Take a tip from marine people that put engines up for the winter.
Fog the engine with fogging oil while running the carburetor dry.
Disconnect the battery.
Now, leave it alone.
About fuel injection (gas or diesel - same) put in a fuel conditioner and run enough fuel so it is up to the injection system. Fog a gas engine by just running it. A diesel can be fogged, but care must be taken that it not run away on the oil.
Matt