autotech2612 Haven't been on here in awhile, except to ask about the Matrix last monthHeard a funny noise two nights ago idling, like I had low oil. Turns out I was two quarts low. Filled to mid-point on stick with Napa 530 synthetic blendI did run the car for 15-20 minutes on the highway the day prior in fourth gear at 55mph with a/c on. Not sure why I wasn't in 5th.Since filling, the car sounds back to normal. I'm now at 268,000 on original engine. Do you really think I harmed anything, considering the car takes 3.4 quarts? Need to keep this car a few more years.