Get the engine up to temperature, or after a longish run, let it idle for about 5-10 minutes, then mash the throttle down. If it kicks out blue smoke, that is where your oil is going. Valve guides and/or seals are shot. Under normal driving conditions you don't notice the smoke as you don't generally idle for 10 mins or more, unless stuck in traffic.
If not guides and seals, it will be knackered piston rings, so get a compression check done to outrule that. Worn turbo bearings can weep a bit of oil into the exhaust as well.
Mobil 1 5W50 is good for reducing consumption, and not a bad idea for engines past 150K anyway tbh.