I think the build up of calcium in the HX is more a function how many hours the engine is run between cleanings of the HX. That being said, it is always a good idea to warm up the engine before engaging the transmission. Repeatedly running a cold diesel engine can cause several problems. Acids can build up in the engine oil, and carbon can build up in the mixing elbow. It's also a good idea to run the engine at full power occasionally for a few minutes, and avoid idling the engine for long periods. End of diesel engine tutorial.
