Busch R-590 is a compressor oil that is or was manufactured by Busch Lubricants. 

In this cross reference tool, PSC offers this Busch R-590 and/or equivalent products of the similar quality and performance. 

See below for the equivalent products and select the 'View Manufacturer Info & Data Sheets' tab for safety data sheets, as well as product data sheets to compare specifications, approvals, properties, and performance characteristics.