Need help with choosing the engine oil

My motorcyle's owners manual says that I have to use SAE 10w-40 oil.. but I can't find an oil bottle with that number..instead I used 20w-40 several times.. a week ago during the service of my motorcycle the mechanic said its better to use just SAE40 than SAE 20w 40 .so the engine is now running with SAE 40... so can you please tell me which one should I use...lowest temperature of my city is around 18°C / 64°F .. But I am planing to travel some places that has a recorded lowest temperature of −2.6°C /27.3°F
Asked Apr 16, 2017
Edited Apr 16, 2017

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