Burning oil smell

On my moms 1998 Chevy camaro you can smell oil burning. I changed the oil at 156,000 or 157,000. My dad is telling me the reason I am smelling the oil burning is because it needs to be changed. I put oil stop in the car because it was leaking oil somewhere. The oil pan had oil on it. My dad had to put 2 quarts of oil in it because it was low. Any idea on what it could be. I don't see oil anywhere that is what is stumping me. Thanks.