If you've ever walked into a trailer at a national drag race, you've probably noticed something interesting. Many of the fastest racers don't carry just one viscosity transmission fluid—they carry several.
At first glance, that doesn't make much sense. Why would someone need multiple weights of automatic transmission fluids (ATF)?
The answer is simple: transmission fluid isn't just a lubricant. In a race car, it's utilized as another tuning tool. The ATF viscosity can influence torque converter behavior, and provide a temporary way to adjust for changing track conditions.
That's exactly why HPL developed the Pro-Series ATF lineup.
The Technical Difference: Viscosity
The difference between Pro 10, 20, 30, 40, 50 and 60 is viscosity (fluid thickness).
As viscosity increases, the fluid becomes thicker, changing the hydraulic coupling characteristics inside the transmission & torque converter.
That means viscosity can influence:
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Converter slip
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Stall speed
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Lockup behavior
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Shift characteristics
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Clutch engagement
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High-temperature film strength
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Protection against shock loads
A thinner fluid generally makes the torque converter act slightly looser, while a thicker fluid generally makes it act slightly tighter.
HPL Pro-Series ATF is generally used by racers requiring the ability to use transmission fluid as a tuning tool. Pro ATF is designed for extreme temperatures, making it ideal for applications frequently experiencing high fluid temps.
Why Turbo Cars Love the Pro-Series ATF
Traditionally turbocharged race cars are especially hard on transmission fluid.
Unlike most naturally aspirated, nitrous and supercharged combinations, turbo cars typically spend more time under heavy load while “spooling” (building boost). This causes the transmission to build an enormous amount of heat.
Heat is the enemy of every automatic transmission.
As temperatures climb, many fluids begin to shear. Causing the oil to become thinner, oxidize and reduce anti-wear capabilities. Affecting converter characteristics, shift quality, consistency and overall transmission life.
The HPL Pro-Series was specifically developed to withstand these extreme conditions. Utilizing a unique and proprietary chemistry, designed to withstand much higher temperatures compared to traditional transmission fluids.
The Trackside Trick: Mixing Pro ATF
One of the unique advantages of the HPL Pro ATF lineup is that all six weights are fully compatible and can be mixed to achieve desired transmission and/or torque converter performance.
Racers often carry multiple viscosities in the trailer for trackside tuning.
Example: Converter Too Tight
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Current fluid: Pro 40
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Adjustment: add Pro 10
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Result: slightly looser converter behavior
Example: Converter Too Loose
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Current fluid: Pro 30
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Adjustment: add Pro 60
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Result: slightly tighter converter behavior
This is not a substitute for having the correct converter. Think of it as a between-rounds tuning aid, allowing you to quickly alter the torque converter characteristics without having to remove the transmission.
The Bottom Line
The HPL Pro ATF series is not a "good, better, best" ladder.
It is a high temperature capable, viscosity-based tuning tool for dedicated race cars.
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Pro 10 = 6.56 cSt @ 100 F
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Pro 20 = 8.51 cSt @ 100 F
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Pro 30 = 10.39 cSt @ 100 F
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Pro 40 = 15.50 cSt @ 100 F
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Pro 50 = 18.13 cSt @ 100 F
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Pro 60 = 23.00 cSt @ 100 F
If your transmission generates extreme heat, or you just need the ability to alter torque converter characteristics between rounds— the Pro-Series lineup answers the call.
