Lubricity and Diesel Fuel Additive Packages

There are a few widespread concerns that we think about as cold weather settles in. As additive manufacturers, we field questions like: How cold can it get before my fuel stops working?” or “What can I do to lower my overall operability?”.

These are the right questions with answers dependent on several factors. While cold weather often makes us focus on things like cold flow, de-icer, wax anti-settling agent, and handleability, lubricity is still just as important as ever.

Critical Applications of Lubricity


With the change to Ultra Low Sulfur Diesels and High-Pressure Common Rail (HPCR) injectors, lubricity is more critical than ever. Diesel engines use fuel to lubricate important fuel injection components. High-pressure common-rail injection systems rely on these parts to move thousands of times a minute under intense pressure and heat. Because of this, organizations like EMA’s and the NCWM recognize the need for a higher level of lubricity to prevent mechanical wear and premature part replacement.

When fuel does not have the proper amount of lubricity, it leads to improper lubrication between moving parts, resulting in premature wear. Eventually, parts can completely wear out, needing early replacement—these replacements are an unnecessary and avoidable expense in most cases.

Even though lubricity takes a back seat to the winterization properties of fuel when it gets cold, it is still crucial. As winter approaches, refiners change how they refine fuel that could lead to a lower lubricity content. #1 blending is also very common to lower the cloud point that leads to lower lubricity content. Several states reduce their bio blending requirements in the wintertime. Since biodiesel is naturally more lubricative, it can also affect the lubricity levels. Often these changes occur without consumer knowledge or awareness of their effects.

Testing and Measuring Measuring

high frequency reciprocating rig used for lubricity testing

How do you measure lubricity? You can measure the lubricity of fuel using the High-Frequency Reciprocating Rig test, most commonly referred to as the HFRR. The HFRR test runs by submerging a metal plate in fuel and rubbing a ball bearing on it at a controlled pressure and rate. At the end of the trial, they examine the ball bearing and measure the wear scar’s size from the friction. A lower number means a smaller wear scar and, therefore, better fuel lubricity.

OK, so what is the proper lubricity level that I will need to ensure my engine is protected? ASTM’s specification for diesel fuel to be sold in the USA states that it must have no higher than a 520 um wear scar on the HFRR test. Major engine manufacturers, and the National Council of Weights, among other organizations, have recognized that no more than a 460 um wear scar is preferred. As a result of their recommendation, 460 um is widely considered the preferred lubricity level for fuels to ensure proper wear protection. 

What can ET Products do?

ET Products designs additive components to work effectively in all engine designs (both modern and older styles) and reach the desired 460 um HFRR rating on nearly all fuel types and sources found in North America.

ET Products laboratory also owns an HFRR machine to continually monitor and test fuel sources to ensure that our chemistry works appropriately to give the desired outcomes our customers require. Many different factors can affect our customers’ lubricity level (biodiesel, #1, refined winter fuel, etc.). That’s why it’s essential to monitor and pay attention to lubricity levels regularly.

By: Seth Rotermund, ET Products