SGO (suzuki genuine oil) 10w-40 premium (its API SG). Drain intervals should be around 5000 km.
Right before each oil change, do an Italian tune-up, i.e. floor it up to redline, upshift and let it decelerate. Rinse up and repeat for about 15 km. As an example you could accelerate in 2nd to 85 km/h, shift to third, and let it come down to 60 km/h. Or, 110-80-110 purely in 3rd gear. Your engine will probably emit black smoke; the smoke means that the engine is getting rid of the built-up carbon.
Its preferable to change the air filter before doing the tune-up; change the oil ASAP afterwards.
Please stay within speed limit; Super Highway might be a good place to do this.
Remember, the car should be at operating temperature before you attempt an Italian tune up; no direct fan, and the thermostat should be working. If the car is prone to overheating, you might want to overhaul the cooling system.