Adequate diesel fuel lubricity is essential for protecting the highly engineered components in modern diesel engines, particularly high-pressure common-rail (HPCR) engines, which are subject to increased wear and deposits that interfere with an optimum spray pattern, reducing power and fuel economy. Many diesel owners add two-stroke oil to their fuel for added lubricity. AMSOIL delivers a better solution that provides additional benefits.

Diesel fuel has traditionally had high lubrication properties, but the desulfurization process that allows fuel to meet modern ultra-low-sulfur diesel (ULSD) requirements also strips it of organic compounds responsible for lubrication. Although the ASTM D975 standard for diesel fuel provides a minimum level of lubricity, it’s not as much as the Engine Manufacturers Association (EMA) has called for.

Due to government mandates for reduced emissions, nearly all diesel fuel sold in North America is ULSD, which contains a maximum of just 15 ppm sulfur, compared to traditional diesel fuel that contained up to 5,000 ppm prior to EPA regulations taking effect in 2006. ULSD is also compatible with modern exhaust treatment devices, such as diesel particulate filters (DPF), that also help reduce emissions.

Because lost fuel lubricity and the expenses associated with fuel-pump and injector replacements are serious concerns among diesel enthusiasts, some have adopted the practice of adding a little two-stroke oil to the fuel to replenish the lost lubricating properties. While this is generally a safe practice, it’s not recommended. Because all two-stroke oils are different, it’s a guessing game regarding how much oil is required to achieve a lubricity benefit. Using too little may not provide any benefit, while using too much may violate EPA laws regarding ash content.

The ASTM D6079 High Frequency Reciprocating Rig (HFRR) lubricity test simulates wear in high-shear conditions, measuring fuel lubricity by rubbing a steel ball on a plate in a bath of fuel and measuring the wear scar. Independent testing reveals Diesel Injector Clean provides superior fuel lubricity over untreated fuel and fuel treated with two-stroke oil.