On a 200,000+km engine?
I used SIN 5 for ~one year on my GT-R with no issues, engine became slightly quieter compared to 10W-50 (HPR10 one service only, ~9,000km). I service my cars every 10,000km, and rather have the GT-R running 50 (hot) oil than a 40 (even though Racing 10 worked fine on track). It's more for my peace of mind knowing an old motor is running a slightly thicker oil when temps are hitting 100°C , although there may not be much difference between 50 and 60. 40 I feel is a bit too thin, especially for summer.