Using a beetle-inspired oil coating, the adhesion performance of a polymer microfiber synthetic adhesive was improved through viscous thin film effects. A 10000 cSt silicone oil layer was applied to polyurethane microfibers 50 mu m in diameter and 100 mu m tall with 100-mu m diameter flat mushroom-shaped tips. Testing showed that the oil layer doubled the adhesion to a 6-mm diameter smooth glass hemisphere, achieving an adhesive strength of 37N/cm(2) given a preload pressure of 6N/cm(2). This work provides a simple method of enhancing the performance of existing fibrillar adhesives.