Abstract: A method of operating a refrigeration system having at least three compressors, in which each compressor has an oil sump with oil at an oil level. The method includes separately connecting the oil sumps of the at least three compressors. Each separate connection allows oil flow only between the oil sumps of two of said compressors thereby preventing bypass flow. The method further includes flowing oil between oil sumps of the at least three compressors and along the separate connections to tend to equalize the oil levels among the oil sumps of the at least three compressors.