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How To Choose the Right Viscosity Oil

Joe Gibbs Driven has a variety of oils to meet your needs, but choosing the right oil for your application is critical. There are several catagories to consider when selecting an oil:

OPERATING VISCOSITY

The “Operating” viscosity is the flow rate of the oil at the normal operating temperature of the oil. Some engines run low oil temperatures, and other engines run extremely high temperatures. Low viscosity oils work well in low temperature applications, and high viscosity oils work well in high temperature applications.

Let’s look at a NHRA Pro Stock Engine, NASCAR Sprint Cup Engine and a World of Outlaws 410 Sprint Engine. These engines will run on different viscosity oils due to the operating temperatures of the engines. An NHRA Pro Stock engine sees oil temperatures around 100F, and it will use XP0 – SAE 0W-5. A NASCAR Sprint Cup engine sees oil temperatures around 240F, and it will use XP1 – SAE 5W-20. The World of Outlaws 410 Sprint engines see 300F oil temperatures, and it will use XP6 – SAE 15W-50. While the oil temperatures and SAE grade oils are very different, the “Operating” viscosity of the XP0 in a NHRA Pro Stock engine, the XP1 in a NASCAR Nextel Cup engine and the XP6 in a World Of Outlaws 410 Sprint engine are very similar.

As you can see, the operating temperature of the oil plays a major role in the selection of the proper viscosity oil. Too high a viscosity oil can result in excessive oil temperature and increased drag. Too low a viscosity oil can lead to excessive metal to metal contact of moving parts. When oil is of the correct viscosity and has adequate anti-wear characteristics, wear due to metal-to-metal contact is kept at a minimum.

Lower oil temperatures require lower viscosity oil.
Higher oil temperatures require higher viscosity oil.

CLEARANCES

It is also important to keep bearing oil clearances in mind. Looser clearances require higher viscosity oil to maintain oil pressure. Tighter bearing clearances require less viscosity to maintain oil flow. Smoother surface finishes allow for tighter clearances, and tighter clearances allow for the safe use of lower viscosity oil for better cooling and improved horsepower.

ENGINE SPPED AND HORSEPOWER

The RPM range of your engine can also effect viscosity selection. Engines that turn more than 9,000 RPM require less viscosity than engines that turn 7,800 RPM. Horsepower also effects viscosity selection. Small cubic inch, naturally aspirated engines require less viscosity than big cubic inch, blown engines. As horsepower output increases, the viscosity requirement increases as well.

QUALIFYING

Low engine, transmission and rear end temperatures during qualifying, permit the use of lower viscosity engine, transmission and rear gear oils to improve lap time and gain valuable starting positions. The chart below provides viscosity recommendations based on horsepower and oil temperature to help you select the correct oil for qualifying and race conditions to maximize your car’s performance.

General reccommendation chart for our line of full synthetics based on standard clearances and normal racing RPM's (max rev above 6,000 rpm):

Looser clearances require higher viscosity oil.
High RPM's (max rev above 8,500 rpm) require lower viscosity oil.



Information and charts are property of Joe Gibbs Driven and cannot be duplicated without permission.