Welch Gold DirecTorr Hydrocarbon Vacuum Pump Oil, 5 Gallon 8995G-20. Welch Gold DirecTorr Vacuum Pump Oil is fractionated especially for use in Welch Direct Drive and Belt Driven Pumps where resistance to chemical attack is required. Gold DirecTorr Oil is checked to insure it meets rigid requirements for proper vapor pressure, chemical stability, viscosity and other essential characteristics. Long experience has proven the wisdom of using it. We recommend that you change your vacuum pump oil at least every 3 months to prolong the life of your vacuum pump.