The Harley Davidson Formula+ oil is a lubricant for the primary chaincase and transmission for Harley Davidson motorcycles. It is a petroleum oil and not synthetic. I believe it is still sold by Harley Davidson, but is only available through a Harley Davidson dealership. I believe most Harley Davidson riders now use SYN3 20W50 to lubricate the chaincase and transmission in their motorcycles, so Formula+ is not as popular as it once was. Formula+ oil viscosity is not listed on the oil container labels. The label says Formula+ oil is tested and certified. The testing and certification is done in-house by Harley Davidson and the Formula+ oil does not have any professional ratings from API or JASO. The official reason Harley Davidson gave for not having an API rating for their motor oils are:
Harley-Davidson® does not recommend any lubricants that have not been tested and approved by Harley-Davidson® engineering because we do not control the formulations. Lubricants are reformulated frequently to meet changing American Petroleum Institute (API) Ratings. API Ratings are developed and tested for use in water-cooled automotive engines and diesel applications. There is no API Rating (classification) for Motorcycle Engines.
Harley-Davidson®, in close partnership with our suppliers, analyzed available petrochemical technology and developed a custom-blended candidate fluid that could be used in all three cavities of a Harley-Davidson®/Buell® motorcycle.The part number for Formula+ is 99851-05.
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