hmmmmmm here is my experience,
I have 2 gli model 15 and 16
2015 is on toyota 5w50 oil and 2016 model on PSO carient 5w30.
2015 gli is on 17k on odo and giving 12km/l in city approx
2016 gli is 10k on odo and giving 13.5 km/l in city approx not less the 13 for sure
Both are on 50 50 hobc and supper from same petrol station.
5W30 car having more engine crisp sound in idle and while acceleration, lighter feel.
surely will be converting other car too over pso carient 5w30 ..... cost effective , oil replacement is 5k with original toyota oil filter.