Daihatsu Sirion?

Sirion 3cylinder petrol engine no smoking exhaust as expected from worn engine .No oil patches where its parked.
No visual leaks in engine compartment. yet uses far more oil than my four cylinder 2lt Peugeot Partner.. When engines are worn large amount of oil breaches oil control rings on the pistons produced an abundance of smoke akin to a smoke bom or gas grenade. where does this oil go when there are no visual leaks. its not high mileage vehicle and mentioned to dealer, answer was "they do use lot of oil.because its 3 cylinder rngine" had I known I would not have let her buy it.. its a dealer I would not use again.