I change the the trans fluid in my vintage bikes A LOT . Oil isn't cheap these days but vintage bike parts can be hard to find and $$$ . Tried just straight , automotive "F" trans fluid but was not happy with it . Did some research and read a lot of threads on vintage forums . Now I buy a gallon of straight 30 wt. non-detergent oil from Tractor Supply Center and mix it with one quart of "F" auto trans fluid . I'm very pleased with the lubrication , wear , and shifting of my bikes with this combo and it is much more economical than the motorcycle varieties of trans fluids . TSC also sells a tractor hyd/trans fluid that I will use if they happen to be out of the 30 wt. . It works very well also but seems " thicker " and makes shifting seem slightly sluggish until after a couple of rides .