Agilent recommends Agilent SY and SANTOVAC 5 oils for the use with Agilent Diffusion Pumps. Agilent SY is a high quality, low cost synthetic organic compound. Its low vapor pressure allows it to achieve base pressures in the low 10-⁸ Torr range. SANTOVAC 5 has ultra low vapor pressure that allows it to achieve base pressures in 10-¹⁰ Torr range and low backstreaming rates.