I have a 99 Chevy Camaro with the GM 3.8 V6. Up to 70,000 miles the car hardly used any oil at all between changes. I have typically changed the oil using the oil change light, which for my driving conditions comes on at about 4500 miles. I have owned the car since new, used only Pennzoil dino 10W-30, and done all the maintenance on schedule. During my last oil change interval, the car started using oil. It used none at 2000 miles, 1/3 quart at 3000, and 1 full quart by 4,000. I swtitched to Castrol GTX from Pennzoil and changed my PCV valve to see if that would help. Instead it got worse, now it used 1/4 quart at 1000 miles, 2/3 by 2000, and a full quart by 3000. This time I got nervous and changed the oil at 3000 instead of adding. Usually these engines are bulletproof and don't have this problem. I am looking for advice on what to use to reduce this consumption, or to find out if anything is wrong that needs attention. Thanks.