HOW HEAT AFFECTS LUBRICANTS: UNDERSTANDING THE ARRHENIUS RATE RULE

Is it true that a lubricant's life is cut in half for every 10 degrees C (18 degrees F) increase in operating temperature?

- 

Yes, this is generally true and is based on a well-established scientific principle known as the Arrhenius Rate Rule.

The Arrhenius Rate Rule Explained

The Arrhenius Rate Rule, named after the 19th-century Swedish chemist Svante Arrhenius, explains the relationship between temperature and the rate at which chemical reactions occur. The rule is pivotal in various fields, including lubrication, which helps predict and manage lubricant degradation.

k = A • e-Ea/RT

The Arrhenius equation is as follows:

Where:

• k is the rate constant of the reaction,

• A is the pre-exponential factor,

• E is Euler's number

• Ea is the activation energy of the reaction,

• R is the universal gas constant,

T is the absolute temperature (in Kelvin).

In practical terms, this equation tells us that the rate of chemical reactions, including those that lead to lubricant degradation, increases exponentially with an increase in temperature. Specifically, for every 10°C (18°F) increase in temperature, the rate of lubricant oxidation doubles, cutting the lubricant's life in half.

Why Temperature Matters