After about 1,500 miles since my last oil change (M1 Synthetic), I checked my oil level while cleaning my car. Much to my surprise, there was just a touch of oil registering on the dipstick. I added half a quart, fired up the engine, checked again and needed to add the rest of the quart for it to be full. This is about the 3rd or 4th time since I've had the car and it has about 37,000 on it (04 WRX). Have I done any possible damage, has this happened to anyone else, is this normal, etc? Please help and thanks in advance.