I had more waiting for car service than I wanted in the past month. I heard the service writers repeat to customers that all modern engines they service and sell - 4 - require synthetic now. Getting all service done by the dealer during warranty has paid for me when issues have popped up later. The dealers seem much better and more competitive these days. I have a Subaru, my wife a Toyota. These days an oil change includes a sincerely decent job of checking the whole vehicle and getting the inside and outside cleaned so I don't consider the dealer a rip off. Even decades ago when I was involved with fleet service and machines our trials with synthetic oil were positive - better in cold, longer engine life. The modern requirement is no mystery to me considering the longevity and performance of modern vehicles. Just look at the output of engines in common modern vehicles. Precision and high performance lubricants are part of it.