Funny how the local dealer service tech years ago shook his head when I told him I was using synthetic 75w-140 differential gear oil in my transmission.
I'm a chemical engineer by training, worked many years for a major oil company, and have extensive experience with production of natural and synthetic oil. The simple truth is that techs receive almost zero training in the specifics of motor oil, mostly b/c it's not needed for their daily duties.
The problem comes from the mismatch between techs' education and the public's assumptions about their knowledge level. Fortunately, most riders on this forum have realized that techs are mostly parts-replacers. Neither techs nor dealers have any desire to change this, since the dealers and HD make more money with more parts replaced, and it's usually faster for techs to replace parts than to spend time on in-depth troubleshooting.
I've seen other videos by this guy, and he's pretty good at a lot of things, yet he admits he doesn't know that much about oil. Ironic considering the title of the video.
