There just isnt a miracle oil additive that will give increased mileage. Lower viscosity is the only way to decrease "drag" from fluids. Modern "Energy Conserving" motor oils already contain a friction modifier that helps the rings scrape the oil away a little eaisier, resulting in a theoretical 1.5-2 percent increase in gas mileage.

Molydisulfide is slightly corrosive extreme pressure lubricant and should probably only be used in gears, not engines. The moly that is used in engine oil does not contain sulphur. It is used as a substitute for zinc.

Redline gear oils claim an increase in mileage, but only for short trips. Once any oil gets up to operating temperature, the viscosity is identical and so is hydrodynamic drag.

Jim