If you are not a city driver and you don't ever drive in dusty conditions and you do everything else pertaining to your vehicle perfectly, you can probably leave your oil in for up to 12,000 kilometres according to most manufacturers. But if you don't meet all these conditions - and virtually none of us does - you should change your oil in half that distance or less. The generally accepted interval is every 5,000 kilometres or every three months, whichever comes first.