That's because there is not any good quality 10w-40 oil available 10W-40 is ideal for winters
For bike use only JASO Certified oil because of wet clutch. it protect clutch especially in high rpm. second use higher API grade like SJ, SL please don't use Obsolete grade. in last viscosity grade use only 10W-40, 15W-40 or 20W-40 don't use 20W-50 in new bike.
instead of changing oil brand in summer and winters, y shoudn't we go for shell ax-3(20w50) in summers and shell ax-5(15w40) in winters????
every bike suites different brand at first we gonna use different one to see how each perform
then which best suites stick with it.
in winters the lower the grade the better and viceversa in summer under pakistani conditions
We have a lots of different bikes in our firm and on the suggestion of our 5s Honda Workshop. We only use Liqui Moly Racing 4t in our bikes. Some of our bike are ridiculously use and abuse by our employees but I am impressed with the performance of the oil and obviously Honda 5s Mechanic who tunned them. We have 7 deluxe for our sales executives and one of them has a mileage of 178,000 kms with first engine and believe me according to the rider it doesn't required anything yet clock to 125 km/h with on economy speed gives a mileage of 51 km/litre on a long journeys doesn't get better than that! I think the model of deluxe is 2010.