I went back to Wheels Through Time this past Sunday. A buddy of mine and I rode up there on our bikes. 222 miles round trip. It was a lot of fun. (Pic below is my buddy. I took the pic. That's my Super Glide. He's riding a Suzuki C50. We were parked at a rest stop on the Blue Ride Parkway.)
I took a closer look at the oil cans this time and picked one up. It was still full of oil. The interesting thing I found was that Harley used to sell their grades of oil using SAE gear lube viscosity numbers. The grades this oil came in ranged from 75 to 140, which translates into motor oil grades of roughly 20 wt to 60 wt. The 75 was for winter and the 140 was for hot summer.
