A high VI is desirable:

• Better wear protection at low and high temperatures
• Easier starting
• Less consumption/leakage

Viscosity Index (VI) is a number assigned to lubricants to describe how much their viscosity changes according to changes in temperature between 104ºF and 212ºF. The VI indicates the degree of change. This is the most important characteristic of any lubricant.

A lubricant with a kinematic viscosity that is midrange (not close to neither the high or low limit) is desirable:

• Helps components work their best
• Lubricant stays in grade

Measure a liquid's flow under the influence of gravity.

Low values indicate improved cold temperature pumpability and flowability. (Oils that thicken too much in cold temperatures won't allow engines to turn fast enough to start.)

• Easier and more dependable cold-weather starts
• Wear/friction reduction
• Longer oil life
• Improved fuel economy

Determines the apparent viscosity of motor oils between minus (-) 40ºF and 32ºF and at high shear rates. (The temperature and shear rate of this test is considered representative of the conditions encountered by car engines cranking in cold temperatures.) The results are used to assign SAE "W" grades.

The lower the pour point, the more useful the lubricant is in cold temperatures.

• Easier and more dependable cold-weather starts
• Wear/friction reduction
• Extends equipment life

Determines the lowest temperature at which the oil flows.

Lubricants with high scores are preferred.

• Maintains their viscosity in the face of high temperature and shear conditions
• Prevents bearing wear

Measures viscosity and the rate of temporary and permanent viscosity loss of an oil under conditions of high temperature and high shear rates. (The temperature and shear rate of this test is considered representative of the conditions encountered in the bearings of car engines in severe service.)

The smaller the wear scar, the better the protection provided by the lubricant.

• Longer equipment life
• Fewer repairs
• Reduced downtime and maintenance expenses
• Longer oil life

Evaluates the friction- and wear-control ability of a lubricant. The Four Ball Wear Test puts one rotating ½-inch diameter steel ball against three fixed ½-inch diameter steel balls, which are covered with the test lubricant, under specific conditions of pressure, temperature, revolutions per minute and duration. Wear scars are measured and averaged.

Lubricants with low NOACK scores are preferred. Low NOACK scores indicate an oil that is less prone to evaporation at high operating temperatures. Low NOACK scores indicates an oil that will keep their original protective and performance qualities longer.

• Better oil circulation
• Maximum fuel efficiency
• Less oil consumption
• Less deposit formation
• Stable viscosity for low and high temperature wear protection
• Fewer emissions
• Longer oil life

The NOACK Volatility Test is a standard test used to measure the evaporation loss of lubricating oils in high temperature service. It provides a basis for estimating the approximate useful life of a lubricant. In the NOACK, a test specimen of oil is heated to 482ºF and held at that temperature for one hour. The pre-test weight of the specimen is compared to the post-test weight, and the test oil's percentage of weight loss is determined.

The NOACK Volatility Test was developed in Germany and has long been a specification test for European motor oils. Volatility testing became a requirement for North American motor oils in 1992, with the introduction of API SH/ILSAC GF-1 oils. Volatility standards were tightened with the 1996 introduction of API SJ/ILSAC GF-2 oils, which required a weight loss limit of 22%. A maximum of 15% evaporation loss is allowable to meet the current API SL/ILSAC GF-3 specifications.

The higher a motor oil's TBN, the more effective it is.

• Suspends wear-causing contaminants
• Reduces the corrosive effects of acids
• Longer oil life

Total Base Number (TBN) is the measurement of a lubricant's reserve alkalinity, which aids in the control of acids formed during the combustion process. Most passenger car motor oils offer only 7 TBN and are formulated with detergents that quickly lose TBN value. With TBN loss, oils lose their ability to neutralize acids, prevent high-temperature deposits and inhibit rust. TBN loss is a primary reason oils require changing. AMSOIL uses highly effective detergent-alkalinity additives in all of their motor oils.

High flash and fire points are preferred.

• Safer to use
• No oil should be heated to temperatures near its flash point

Flash point is the lowest temperature at which a flame causes vapors to ignite. Fire point is the lowest temperature at which burning is sustained for five seconds.