My Regal (3800 nonsupercharged) has the GM oil life monitor, but mine doesn't have the "driver information center", which was optional on the car. So instead of the informative readout I have a light that comes on which says "Change Oil Soon". There is no % reading. So if I drive it until that light comes on, what % would that be equal to? I'm wondering how soon after that light comes on does the oil need to be changed, because I only have access to a garage on weekends, and if it came on Monday morning, I could easily go 350 miles before the next change. The owner's manual just says it should be done "soon".