Whenever I ask our mechanics at work, (maintain mass transit fleet) or the mazda dealer for my wifes car, or the A.S.E. Master Mechanic that does my work, they all say using synthetic is not worth the money if you perform the manufacture's scheduled maintenance. Now if you abuse it, i.e., oil changes once a year, that kind of crap, then synthetic is proable worth the expense. Any A.S.E. mechanic's in the group want to weigh in on this? I'd sure like to know.