All old diesels smoke a bit when first started up, more so when it is colder. However if the smoke is blue it could be oil, but you said your oil consumption went down so I don't think you are burning any oil. Does it run a little rough at first? How much smoke? When the valve guides wear they can spew a nice cloud of dark blue smoke, my Toyota did this. Mine smokes a little in the morning, it is light gray. But maybe it could be blueish if the light hit it right, diesel is an oil. I will have to look more closely tomarrow morning.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200