My cars smokes occasionally..exactly as you described. Over a preiod of time ( a few months)..the engine oil level will dip low. Keep a close eye on the engine oil level. I had to refill nearly 2.5 litres last week, after the white smoke raised its ugly head....!!
Heard from one of the mechanics, that it has to do with the CO2 Sensor settings. Or is it CO settings...? Not sure. Will do more research and get back.