@ammarzahid, although i agree with the recommendation to use such oil for winter that are less viscous at ambient temprature, I have a question. According to Owners manual, the minimum temprature given against viscosity is
-20? C : 10w-.......
-10? C : 20w-.......
while in Pakistan where most of areas barely touch 0? C, that too in extreme winters, we still have a margin of 10? C to use 20w-50 round the year. Still many people prefer and recommend to use 10w-...... oils (5w & even 0w oils for cars) during winter season. Is the practice worth following ?
P.S. this thing is not asked in particular reffence with GS-150 because the manufacturer's recomendation is 10w-40.
(i tried to add degree centigrade symbol but it unfortunately appears as ? )