Switch to Mobil 1, now burning oil?

[Grdenko]

last week i changed my oil with Mobil 1 0W-40. before, i was always running pennzoil 5W-40. since the switch, i have noticed im burning oil, there is blue smoke and the smell. its mostly when i first start the engine, it doesnt burn as much when its warm.

someone told me that switching to sythetic on an engine with over 100k miles will cause that, but that doesnt make sense to me. the engine never burned ANY oil before.

do i need to switch to a higher weight Mobil 1? or do i need to go back to dino oil to make this stop? will burning oil in itself cause any damage to the engine?

thanks