The Mazda dealership is 5min from my place, they change the oil with their moly brand. I only pay for labor for the next 7 years, oil and filter are free. So, being under warranty, if their moly "does have" more iron in it and puts noticeable wear or damage to the engine guess who fixes it? Mazda. Oil reviews and types are mostly over-rated. Use and good brand, change at the specified times and you'll be good.