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What are Friction Modifiers?
Please explain what Friction Modifiers means? Example: Mobil 1 Synthetic Gear Lube LS 75W-90. So LS means it has more Friction Modifiers. Does "Friction Modifiers" mean it has more slippery for LSD's or that it contains more friction for the LSD clutch plates (hence potentially more LSD locking performance)?
-- Steve Lau, San Jose, CA
Friction modifiers are designed to do what the name implies, they modify friction. In the case of a Limited Slip Differential (LSD), the friction modifiers are designed to modify the friction characteristics of the fluid such that clutch engagement occurs when you need it for the rear differential to allow the rear wheel to rotate at different speeds. For example, if a vehicle is on an icy road and one wheel is on ice and slipping with no traction, in a normal differential the other wheel would be left with no torque because the one wheel is spinning. In a vehicle with LSD, even though one wheel is spinning, that spinning action causes the clutch to engage the gear (the friction modifiers in the lubricant enable the smooth engagement and disengagement of the clutches as needed), which produces the torque required to power the non-spinning wheel, enabling the car to move.