When you say "uses motor oil"... how much? Also, how does it run? (good power, quiet, etc) The smell test is a good one, coolant smells like coolant... diesel smells like diesel ... and oil smells like oil. Obviously if you're going through a litre of oil every, say 800km and you're not leaking any, you're burning it. Rings, valve guides and/or turbo seals can be a source of the oil "supply". If the engine sounds good and has good power but goes through oil, I might investigate the possibility of needing a turbo rebuild. How long have you had the truck, and have you done an oil change? My truck, which I presume is used in more or less the same climate, rarely emits white smoke for more than a few minutes on even the coldest days. A faulty head gasket will cause white smoke that never goes away, but that doesn't explain the oil in the intake. I'm no turbo guru, but substantial amounts of oil in the intake seems to indicate a problem. Good luck, Tony