Pardon the stupid question, but honestly I am not very knowledgable when it comes to automotive mechanics. My check oil level message came on today and I only have 3,500 miles on the V. Sure enough, the level is low, which seems odd to me since I don't see any leaks. Is this normal? The only mod I have is a Magnaflow exhaust, which I installed approximately 1500 miles ago. Since then, I've also noticed that the inside of the exhaust tips has been turning black. Does this mean the car is running rich? If so, what can I do about it? Thanks in advance for any feedback.