I use the pinch test to decide if an oil has a good film strength. I put a drop of oil on my finger and squeeze as hard as I can with my thumb then try to slide my thumb across my finger. If it grabs the test is a fail,if it slides then it's a pass. I know it's not a truly scientific method but works when you're in the store trying to determine if the oil you're looking at is something you may want to pour in your motor.
The scientific method to determine film strength is done with two hardened,polished steel plates,a press and a force gauge. One plate is held stationary and one plate slides. A ram with a roller is pressed down against the sliding plate with a measured amount of pressure and a force gauge measures to amount of effort it takes to slide the moving plate. A film of oil is applied to the plates and pressure is applied and the force is measured to slide the plate. Incrementally more pressure is applied and the force is measured. This is repeated until the pressure applied stalls the movement of the plate.
The point of stall is the film strength for that given oil.
My pinch test has determined that these ultra light oils that are being recommended by the manufacturers have really poor film strength. 10w-30 is about as light as I would recommend for a splash oiling system. 10w-40 for a pressure system.
There is so much varying information about synthetic oils that I don't know what to believe. Some say the base stock is plant based oils. Some say the base stock is crude that has been homogenized so all the oil molecules are the same size. I know highly refined crude oil and ZDDP has made my engines run for hundreds of thousands of miles.
The scientific method to determine film strength is done with two hardened,polished steel plates,a press and a force gauge. One plate is held stationary and one plate slides. A ram with a roller is pressed down against the sliding plate with a measured amount of pressure and a force gauge measures to amount of effort it takes to slide the moving plate. A film of oil is applied to the plates and pressure is applied and the force is measured to slide the plate. Incrementally more pressure is applied and the force is measured. This is repeated until the pressure applied stalls the movement of the plate.
The point of stall is the film strength for that given oil.
My pinch test has determined that these ultra light oils that are being recommended by the manufacturers have really poor film strength. 10w-30 is about as light as I would recommend for a splash oiling system. 10w-40 for a pressure system.
There is so much varying information about synthetic oils that I don't know what to believe. Some say the base stock is plant based oils. Some say the base stock is crude that has been homogenized so all the oil molecules are the same size. I know highly refined crude oil and ZDDP has made my engines run for hundreds of thousands of miles.
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