You need a grease that is waterproof & very tacky which can hold itself to the urethane bush. It needs to have good lubricating properties and not be absorbed into the bush which can damage the bush. In most cases the bushes should be made of a high-quality heat cured PTMEG Polymer which is resistant to petroleum products like fuel and oil. That being said we found that the best grease for this is a silicone-based grease.
Silicone based grease or lubricant is very tacky and sticks to just about everything, from polyurethane, to zinc coated sleeves, to bare skin. This is the main reason many poly bushing manufacturers use a silicone base in their grease. A common additive to that base is PTFE (polytetrafluoroethylene) since it lowers friction and is completely waterproof, both things you want in a lubricant. PTFE does not mix well with oil, or any other liquid, but it holds silicone lubricant to polyurethane bushings and sleeves very well, making a tough, sticky combination.
SuperPro Silicone (PTFE) Grease is specifically engineered to compliment the already outstanding performance of their polyurethane suspension bushes. The environmentally-friendly grease requires sparse application, making it cost effective to user. It offers nil-penetration into polyurethane, resulting in zero breakdown of the bushing, in turn providing consistent lubrication and exceptional wear-life.