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Re: Harley Oil 58, 75, 105

PostPosted: Thu May 30, 2019 8:04 pm
by 57XL1002
Here is a worthwhile primer on motorcycle oil for those who assume that everything is better with Blubonnet On It. http://www.motorcycleanchor.com/motorcy ... tml#WYRNTK It also relates to Dave's curiosity of why HD used the peculiar Oil Grading (SAE)(API CLASS RATINGS)( JASO-MA specification) system they did. Oils are rated at both flow and lubricity (?) at certain oil/engine temperatures. The low end of the spectrum is 40*c (about 100*F) and the upper end 100*c (about 210*F). 58*c = 136*F, 75*c = 167*F, 105*c = 221*F. This basically is how multi viscosity oil is graded, at the low 40*c and high 100*c levels. Also why we have oil coolers. I know we wern't into metrics then, but science was. Most of this is just my guesswork, without the original engineers to explain their reason, there is nothing else left to do. I'm 72 and been professionally involved in racing for over 50 years, and the best advise I always gave my customers is, never drop the hammer till you see 180* on the temp guage uno peso...

Re: Harley Oil 58, 75, 105

PostPosted: Thu May 30, 2019 9:11 pm
by hennesse
And here's another example of Harley 75 = SAE 40.Look here AMF, perhaps later 1970's ???

Re: Harley Oil 58, 75, 105

PostPosted: Fri May 31, 2019 9:21 am
by Bubbalowe
www.bobistheoilguy.com/viscosity-charts/

Viscosity comparison charts show overlaps between Saybolt and API. MOCO used SUS in olden days.