Diester, polyol ester and aromatic ester base stocks can withstand the extreme temperatures and pressures created by air or gas compression. The lubricant must prevent corrosion and wear while acting as a sealant. Synthetic esters are selected to be compatible with the gas being compressed, as well as the metals and elastomers used in the system.The optimum synthetic ester will have low vapor pressure and sufficient viscosity at peak operating temperatures.