(NOTE: this answer covers both engine and primary/transmission lubricants, since the question did not specify which was of interest.)
The recommended engine oil for this bike is Harley-Davidson's proprietary "Genuine" brand engine oil. However, many aftermarket oils are available. If you use an aftermarket oil, make sure it is labeled "for use in Harley-Davidson motorcycles" to make sure additives, temperature tolerance, etc., comply with Harley requirements. Automotive motor oils are NOT recommended for Harley engines. In a pinch, if you need oil NOW and can't find a Harley shop (or a shop selling aftermarket "for Harley" oil), the manual recommends using the proper weight motor oil specified for use in DIESEL engines. Recommended viscosity is 20W50 for all normal conditions. Oil capacity for the rigid-mount Evolution Sportster engine (1986-2003, 883, 1100 and 1200cc) is 3 quarts.
The recommended primary/transmission oil for this bike is H-D "Sport-Trans" fluid, which is a specialized lube formulated to work with the wet clutch. H-D discontinued this fluid, and it is now superseded by "Formula+" fluid, which is a "universal" fluid for transmission and primary drives in both Sportsters and Big Twins. Many aftermarket primary/transmission oils are also available; if you use one, be sure it's labeled for use in the Sportster transmission, as the lubricant for the Big Twin transmission may not work properly with the wet clutch. Transmission capacity is about 0.8 quarts, but varies from one bike to another.
should be 20-50 wt harley oil but check with your dealer first..
what type of oil for a 1993 Harley Sportster 883
harley recommends 20/50
Three
A type of primary oil that can b used for a Harley Fat Boy is Lucus Primary specific oil & Lucus 85/140. This can be purchased at auto repair shops.
Tis underneath the transmission on the left front of the square oil tank.
20w50 motorcycle oil
3 1/2 quarts.
Right side of bike by the seat is the oil tank pull out round dip stick
80/90 semisynthetic hypoid gear oil is what the factory put in it but I use Red Line Heavy ShockProof fully synthetic gear oil. Not cheap but neither was your Harley.
In the compartment under the seat on the other side from the oil reserve
good site