Ok did some reading on this form as well as online and castrols web site and I think kona is right. Non synthtics don't last as long. There is no ill effects of switching fron synthtc to non synthetics. However synthetics are better protection for your engine and will last longer. And yes snthetic blends will also be normal expensive. However synthetics yield better performance than non synthetic blends. Thanks guys, learn something everyday.
2013 V6 Mustang Automatic with the following mods: Roush Hood scoop, 3M Clear braw paint protector, MRT rear window louvers, 3M scotchprint carbon fiber roof wing decklid and scoop, strut tower brace, FRPP axleback exhaust.