i wouldn't do the thicker oil, then you'll starve the top end and run into a whole other set of issues and possibly trash the overhead. Oil galleys on the top end are pretty small and that thick of oil wouldn't get up there quick enough when it's cold. I would stick with the recommended 10/30 or 15/40 at the most.
Generally if you have oil smoke the color is more grayish and not white and the smoke lingers more and you'd smell it. Sometimes it's hard to tell though but the lingering effect of the smoke is an indicator, coolant steam goes away quickly, oil smoke tends to linger around longer before it dissipates. With 12k hrs it might be a oil ring issue maybe. You'd generally have low compression during a compression test though. Generally.