Synthetic lasts longer between oil changes....if you are a "maintenance super hero", there's no need for it. I pulled apart my original Mustang motor after 250,000 miles, running only the cheapest conventional oil (using police/severe duty maintenance schedule) and it looked like you could eat off of it...no sludge whatsoever. High zinc (as found in high mileage oils) is a good idea for cars without catalytic converters.