Amsoil 0w-40. Recommended by Amsoil, covers most of the temperature band. Honda can’t deny for oil issues by law.
Thank you for contacting AMSOIL with your question.
For the temperatures that you experience, I would suggest using the 0W40 Powersports Oil (product code AFF). This will cover the broadest temperature range so it will crank over easier in cold temperatures. As far as warranty goes, being it is an extended warranty, you would have to read the verbiage in the contract to see what is required of you. If it states that you have to use a certain oil, then you would have to abide by that. However, Honda cannot void the manufacturer’s warranty that comes with the machine for using a different brand of oil as that would be against the law.