If your a costco member, you can have a case of Castrol Grand Prix 10W40 for Motorcycle oil 12 x 1 L shipped to your door for $56.99, that works out to $4.75/L.
Costco link is HERE
SAE 10W40 motor oil should only be used in vehicles where SAE 10W40 motor oil is recommended by the manufacturer. Please consult the vehicle manual.
Castrol Grand Prix quality engine oil specially developed to maintain its lubricating performance over the entire drain period and provides the necessary level of long term engine protection. It has been specially designed for a wide range of single cylinder and multi-valve, multi-cylinder 4-stroke motorcycles under every day riding condition
Features:
Durable protection against engine wear throughout the drain period
Combustion chamber and piston cleanliness
Protection against harmful engine deposits
Controls oil consumption
Good gear shift and wet clutch performance
Mineral based 4-stroke engine oil
Meets or exceeds API standard SG
12 x 1 L
Costco link is HERE

SAE 10W40 motor oil should only be used in vehicles where SAE 10W40 motor oil is recommended by the manufacturer. Please consult the vehicle manual.
Castrol Grand Prix quality engine oil specially developed to maintain its lubricating performance over the entire drain period and provides the necessary level of long term engine protection. It has been specially designed for a wide range of single cylinder and multi-valve, multi-cylinder 4-stroke motorcycles under every day riding condition
Features:
Durable protection against engine wear throughout the drain period
Combustion chamber and piston cleanliness
Protection against harmful engine deposits
Controls oil consumption
Good gear shift and wet clutch performance
Mineral based 4-stroke engine oil
Meets or exceeds API standard SG
12 x 1 L