0w-20 is the best recommended engine oil viscosity grade by Pak-Suzuki as per Cultus's Maintenance Manual.
17000 km is not that much mileage and you can choose a lower viscosity oil as this time, after 80k or 100k km it is not that recommended to change viscosity.
You will feel a very big difference by switching to 0w-20 from 10w-40. 0w-20 oil stays thin and flows easily through the engine even at high operating temperatures and in hot weathers so it puts less load on the engine and is more suitable for hot weathers.
Hence, as recommended by the vehicle manufacturer you should use 0w-20, or if not atleast 5w-30.