Motor oil's protection against the wear and tear of steel engine parts takes effect only at high pressures, according to a new study.
The analysis reveals the molecular behavior of a common lubricant additive, whose mode of action had remained mysterious since the additive's introduction in the late 1930s. Understanding the additive's action may lead automotive engineers to design more environmentally friendly lubricants for steel as well as products especially suited for lighter, more efficient aluminum engines.
Zinc phosphates have long been the most common lubricant additives for protecting steel parts, such as pistons and cylinders in car engines, against wear when they contact each other. Through trial and error, researchers have looked for new additives, but none has outshined the zinc phosphates.
"People traditionally tried a whole bunch of lubricants and found that some worked and some didn't, but it wasn't always clear why," says Mark Robbins, a friction