AbstractThe results of work intended to produce inexpensive, synthetic lubricants compatible with R‐134a using waste carboxylic acids C4‐C6as the base are presented in this paper.The suitability of the products synthesised was first evaluated considering their physical and chemical properties, and their thermostability determined by the standard Philipp test (sealed glass tube method). Two ester bases were then selected for further testing — a pentaerythritol esterified with C4‐C6monocarboxylic acids and a polyalkyleneglycol similarly esterified with monocarboxylic acids C4‐C6.The base oils chosen were tested for their corrosive action on metals in the presence of water in different concentrations. The pentaerythritol ester proved to have the most advantageous properties at that stage. The results of the laboratory tests have been corroborated by trials conducted on real refrigerating compressor systems. Only the lubricant that was obtained using pentaerythritol esterified with monocarboxylic acids C4‐C6as the base withstood the