Good mineral oil will last for 5K if good quality Oil filter and Air filter is used. You can check manual as well as Concerned 3S dealers for drain interval. People usually interchange 3,000 as interval because 3,000 is miles for drain interval of mineral oil which is equivalent to 5,000 Km
For synthetic, it can easily last upto 7.5K - 8k . If u will change it early, purpose of using synthetic will not be achieved 100% as most of them contains compound for cleaning which which starts working at full when it starts getting little dense I.e around 5000K.
Dr. SAAB is too innocent and cunning 3s dealers like Macca motors have ripped him easily(No problem bro, I have also ripped off by them since1998-99 at their opening) @abid110 bhai is right, this suzuki ultimate oil(infact all API SL/SM engine oils) has low zddp while Suzuki Premium is for old engine have high zddp value which is must for Cultus Engine