Well, you say that the colour of the smoke is blue? Usually that means engine oil in the smoke. Unburnt diesel fuel and the colour would be more white. Restricted air filter or a high load on the engine would cause black smoke. How long has it been since an oil/filter service? Are you using correct engine oil, ie a diesel oil with a CD or CF or higher rating? Is the oil level reading high? DutchySorry guys, been out of town and just got back. The smoke is blue, I assume it's the glow plugs. How many are there on a 08 ck35 hst? If more than one, should I go ahead and change them out while I'm there? Thanks again.