i know on newer vehicles manufactures suggest anywhere from 3000 to 9000 miles. i dont have a manual to look in.
how often should i change the oil every ---- miles? on 2002 Suzuki Grand Vitara
About every 6000 miles or at least once a year if you don't put many miles on.
According to the manufacture under normal usage it's 7,500 miles or 8 months. Under severe usage every 3,000 miles or 3 months. That is what Suzuki recommends. I strongly suggest you go to a semi or full synthetic lubricant. A viscosity of 5-30W is what Suzuki recommends.