So Harley says use Formula +, or a synthetic 20/50 in the transmission. Somewhere along the line I got the idea that a 90 weight gear oil is roughly the same viscosity as a 50 weight motor oil. And there is plenty of people saying that a 75w-90 is thicker than a 50 weight motor oil.
That doesn't seem to be true. If you look at the specs on mobil 1 75w-90 and Valvolines Syn 75w-90 you find that they are no where near a 50 weight on the viscosity chart.
Understanding that the transmission is going to create shear issues with oil. Is that why they recommend a 20/50 syn, but not a 20/50 dino?
Wouldn't a straight weight 50 accomplish the same thing that a thinner gear oil is going to do?
That doesn't seem to be true. If you look at the specs on mobil 1 75w-90 and Valvolines Syn 75w-90 you find that they are no where near a 50 weight on the viscosity chart.
Understanding that the transmission is going to create shear issues with oil. Is that why they recommend a 20/50 syn, but not a 20/50 dino?
Wouldn't a straight weight 50 accomplish the same thing that a thinner gear oil is going to do?
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