I bought this car as a carryover this April. It had 40 miles on it and was built 15 months before. The battery was no good after sitting at the dealers 'overflow' remote lot. Anyway, all was fine as I used it as normal transportation. I changed the oil and filter at about 900 miles with an OEM filter and used 5-30 Mobil ! as summer heat approaching. The engine burned no oil and was only slightly darkened at 900 miles. I recently changed oil and filter again at about 4500 miles. The oil was still at the full line, but looked fairly dark on the stick. There was no apparent fuel smell on either oil change, but with this last oil change the oil is coal black. I'm not used to seeing this as the car is not particularly short tripped and no condensation in summer driving. The engine has no odd mechanical noises and power seems ok. I'm puzzled with this situation. Is this a high pressure fuel injection deal or some other issue? Thanks for any insights.