I have been running full synthetic in all of my engines for at least 10 yrs now... At first I was skeptical but after seeing how clean the oil has become between changes AND how GNARLEY the oil in my fathers engines are with CONVENTIONAL oil, Im sold...

Additionally, my friends that own a large transmission/powertrain shop tell me that they can ABSOLUTELY see a major difference in the wear characteristics on the big landfill trash truck transmissions/quarry trucks/UPS truck manual gear boxes/rear differentials where they have switched to full synthetic in those shops...

I do know that without ZINC and other additives, your chance of a flat tappet cam failure is quite high ESPECIALLY in the break in period...

Thats all I know about engine/gear box oils