5W30 is suitable for operating temperature between -25°C and 25°C, and 5W40 has a range of between -25°C and 35°C. In terms of oil flow, 5W30 has greater flow than 5W40. However, for providing higher pressure, 5W40 is superior. Out of the two engine oils, 5W30 is lighter, offering better fuel consumption.
Kev