The One Arm Bandit - Uncovered and Unplugged

Note: This write up on the Falex extreme pressure demonstration tool is being provided to help educate AMSOIL Dealers on the reasons why this device should not be used to measure the performance of engine oils. AMSOIL has received many complaints about competing oil companies and their use of this device in an effort to discredit the performance of AMSOIL products and enhance the performance claims of their own products. AMSOIL Dealers should never consent to having our products manipulated in this device, nor should they attempt to use this device to enhance AMSOIL performance specifications or to discredit competing manufactures products. The information provided below can be used in an informational fashion to help “clear the air” with regards to the validity of data generated by the ”One-Arm Bandit.”


Q. A demonstration at a recent trade show used an apparatus called the One-Arm Bandit to compare the wear protection properties of different motor oils and additives. Is this an accurate method of measuring wear protection properties?


A. The Falex manufactured extreme pressure demonstration tool, also known as the “One-Arm Bandit,” is used to showcase the properties of extreme pressure (EP) additives and attempt to create a need for the performance benefits of the EP additives in fully formulated engine oils. The One-Arm Bandit is not an accepted test by the American Society for Testing and Materials (ASTM) and is too variable to differentiate between samples. Instead, the Standard Test Method for Wear Preventive Characteristics of Lubricating Fluid (Four-Ball Method), designation D-4172, is recognized by the ASTM and is used to evaluate the anti-wear performance of lubricants.¹ Moreover, engines operate in an environment with boundary and full fluid film lubrication where good anti-wear properties are required and extreme pressure properties are not necessary, and may actually be harmful to overall engine performance and longevity.


The One-Arm Bandit can be manipulated with different operating parameters to significantly change the output and can make one believe an engine oil or oil additive is required for maximum engine protection. There are two direct factors that can be influenced, the type of applied force and the bearing wear surface presented.


Immediate vs. Gradual Force


Anti-wear additives are heat-activated, and applying immediate force does not allow enough time for heat to build up to activate the additives, resulting in metal-to-metal contact.
When the lubricant cannot withstand the pressure, the machine will seize. When immediate pressure is applied, generally 30-40 foot-pounds of pressure (torque) is achieved before seizure.
When gradual force is applied enough heat is built up to activate the additives. More pressure will be achieved when gradual force is applied due to the extra time allowed for the chemistry to create sacrificial wear layers.

Slowly applying pressure allows the machine to reach upwards of 90 foot-pounds before it seizes, or in some cases, it will not seize at all.

Applying a higher amount of force before failure with different oils and additives can give the illusion that an additive provides better long-term anti-wear protection. The concern with this attempt to link EP performance with long-term engine wear is that engines typically do not experience exceedingly high amounts of pressure because they operate under boundary and full-fluid film lubrication. Furthermore, the negative effects EP additives have on the overall balance of engine oils are not communicated with the One-Arm Bandit results.


Flat Wear Surface vs. Fresh Surface


The larger the bearing contact area, the more load the oil can support. The bearing used in the EP demonstrator quickly develops a flat spot after being held against the rotating element. If it is not replaced or rotated after every demonstration, the contact surface on the bearing increases and the same oil can now withstand more pressure, yielding a higher pressure reading.
A bearing with a flat spot can withstand up to three times the amount of pressure a new surface can.
A fresh bearing surface is both cylindrical in shape and clean and free of additives, as opposed to a used, flat surface that has layers of the additive build-up. The additional layers of the anti-wear additive will skew the oil performance, yielding a higher foot-pound reading.
A fresh bearing usually can withstand 30-40 ft-lbs, whereas an old bearing with a large flat spot can withstand upwards of 60-90 ft-lbs.
Potential Catastrophic Effects of Aftermarket Oil Additives:


Aftermarket oil additives are not necessary in fully formulated oils. In fully formulated, high-quality engine oils, additives are carefully balanced to be synergistic, performing well together. Tampering with the balance by adding other chemicals can adversely affect overall oil performance, sometimes dramatically.
Some oil additives contain extreme pressure (EP) agents that can be harmful to engine components. Oxidation inhibitors, detergents, and corrosion inhibitors compete for surface area and are sacrificed when EP additives are added to fully formulated oil, leading to sludge, corrosion, and oxidation.
Some engine oil additives use chlorine in the form of chlorinated paraffin (chlorinated wax), which when united with hydrogen, can form hydrochloric acid (HCL). Hydrogen chloride formed in the presence of larger quantities of moisture can cause severe corrosion of the metal surface.² Chlorine-based additives can be film forming even at ambient temperatures, but as the temperature rises, they become more aggressive and, with the release of HCL, can cause significant corrosion.³ Chlorine additives are not considered a viable option for modern lubricants.? 

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