My 2002 Cavalier was on a one-year p/t warranty when I first got it, and I HAD to change the oil every 3750k miles (6,000 km's). Used whatever 5w30 conventional that happened to be available where I went. I tend to change depending on the weather and driving conditions; so during last summer I stretched changes out to about 8-9,000 km's as I was doing a lot of highway driving. Still, that was less than 2 months! Now my wife and I are doing mostly short trip city driving, so I am planning on changing again early in January when the weather starts getting much colder, and that will be about 6,500 km's/2.5 months into this change. Will probably use Pennzoil 5w30 or Petro Canada Supreme 5w30, as they both have good cold-weather properties....