I recently purchased a used 05 Sonata with a V6 2.7 liter engine. The car has 101,000 miles and runs great with no issues. The problem I have is when I initially start the engine after it has been sitting for awhile it is very noisy. The valves seem to be rattling excessively until the car runs for a few minutes and then quiets down. The oil is about a quart low but looks clean. Does anyone have any idea what I can do? Should I change oil? Does it sound like the seals have gone bad?