For decades I was involved in touring motorcycles and we had endless debates over engine oils. Unlike most Corvettes, we put big milage on our bikes every season. I had more than 100,000 km on each of three Honda Goldwings. Eventually, a US publication commissioned a lab to do a series of tests on synthetic oils. The tests were limited to the 5 or 6 well known national brands. They tested for all the usual things and even simulated a 100,000 miles of usage. In the end there was no measurable difference between the various brands. Interestingly they also had one premium brand regular motor oil. While there were some differences in things such as additives there was no measurable difference in the 100,000 mile wear test. The one big difference was the synthetics had better viscosity in cold starts, especially sub-zero starts.
