SIGNIFICANT CHALLENGE FACED by today's motor oils is maintaining an adequate level
of protection during high-temperature conditions. Without a quality motor oil protecting
it, an engine can be damaged through motor oil breakdown, viscosity increase, and deposits
- all caused by excessive heat.
All motor oils are subject to vaporization when exposed to high heat. How much an
oil vaporizes is measured by the NOACK Volatility Test (ASTM D5800). Conventional motor
oils tend to vaporize the most, the lightest fractions evaporating first and leaving
behind a thicker, harder-to-pump motor oil. The uniformly sized molecules of synthetic
motor oils are much more resistant to vaporization. Less oil evaporates and viscosity
The flash point of a motor oil is the lowest temperature at which application of a
flame will cause lubricant vapors to ignite. Higher quality base stocks exhibit higher
flash points, and the higher a motor oil's flash point, the better the protection.
AMSOIL motor oils are formulated with high flash points, keeping volatization to an
absolute minimum and maintaining their superior protective and performance qualities
in extreme heat conditions. In fact, a look at the chart shows AMSOIL 10W-30 Synthetic
Motor Oil loses significantly less of its original weight during high-temperature service
when compared to competing motor oils.
As motor oils operate in high heat, especially over extended periods, they tend to
thin out and lose their ability to provide adequate wear protection. Viscosity Index
(VI) indicates the degree of an oil's viscosity change over a given temperature range
(between 40°C and 100°C). The higher a motor oil's VI number, the better it
is able to maintain its viscosity over a broad temperature range, translating into
better wear protection in both hot and cold temperatures. Motor oils with a low VI
do a poor jog of maintaining viscosity in extreme temperatures, while they are very
thin at high temperatures.
Motor oils formulated with synthetic base stocks usually have naturally high VI numbers,
giving them the ability to resist viscosity change in high-temperature operation.
Conventional motor oils, on the other hand, require high amounts of VI improvers that
increase the relative viscosity of motor oils during high-temperature operation. Viscosity
improvers can be thought of as springs, coiling at cold temperatures and uncoiling in
high temperatures. Uncoiling makes the molecules larger, increasing internal resistance
within the thinning oil and reducing the overall viscosity loss of the fluid.
Viscosity Index Numbers
Less than 60 -
Poor quality and monograde oils
60 to 95 - High quality mineral oils
Greater than 95, but less than 120
Very High (VHVI):
Greater than 120, but less than 140
Ultra High (UHVI):
Greater than 140
AMSOIL Synthetic Motor Oils have "ultra high" viscosity indices, allowing them to
stay in grade and provide superior wear protection throughout extended drain intervals.
In fact, AMSOIL 10W-30 Motor Oil was recently subjected to a triple length Sequence
IIIF test. Even after being subjected to the test three times longer than the standard
length, AMSOIL 10W-30 performed three times better than the standard limits. The
competitor's motor oil showed dramatic viscosity increase in less than half the time.
Oil heated in the presence of air oxidizes, forming damaging acids and deposits.
The higher the temperature, the higher the rate of oxidation. Oxidation inhibitors
are added to motor oils to minimize the high-temperature deterioration process, while
detergents and dispersants minimize the formation of sludge and deposits, neutralize
acids and hold solid contaminats in suspension.
AMSOIL Synthetic Motor Oils are formulated with the highest quality additive packages,
resisting the damaging effects of heat and oxidation much longer than conventional motor
oils, and keeping engines running clean and deposit-free.
Part 2 - Cold Temperatures