I have a 2000 GT with 155xxx miles. I know I need to be changing the oil every 3000 miles on the dot, but this month I haven't had as much income as normal due to school starting. I went 4000 miles between my last oil change, only 1000 after what it should have been. I burned 2 quarts of oil in that 4k miles. I'm not sure what causes burning of oil exactly, but any info is appreciated.