11-09-2017, 07:09 AM
My OEM Honda Service Manual (and I think also the owners manual) suggest different oil for 2 different temperature ranges:
15°C and below: 10W-30
10°C and above: 10W-40
As most motorcycle are only ridden in the season, when it's not too cold, it makes totally sense to the shops, to provide just 10W-40, same here in Germany. Also these ranges do fairly overlap.
I used 10W-30 during the dark time of the year and 10W-40 from May to October.
However, I don't think, it's critical and either will work.
15°C and below: 10W-30
10°C and above: 10W-40
As most motorcycle are only ridden in the season, when it's not too cold, it makes totally sense to the shops, to provide just 10W-40, same here in Germany. Also these ranges do fairly overlap.
I used 10W-30 during the dark time of the year and 10W-40 from May to October.
However, I don't think, it's critical and either will work.