We are planning a trip in our Ecotec powered '03 Cavalier later this month and the oil will have about 2,800 miles on it when we start. I changed it in March to dino 5w30 Chevron, which is what it has seen since new. Round trip will be about 800 miles of mostly highway driving. The car normally sees mostly highway miles. I will do a UOA later this year but my gut tells me that 4K should be an ok interval for this oil and car.