Bio-diesel inherently has better lubrisity.
Right now there is no required standard but it is on the way- read below.
by
Maurice E. LePera
LePera and Associates
In October 1993, EPA limited sulfur in diesel fuel for “on-road” vehicles to a maximum of 0. 05% or 500 parts per million (PPM). This created many fuel related problems that resulted from the poor lubricating quality of the low sulfur diesel fuel. Since the maximum limit for sulfur in diesel fuel prior to October 1993 had been 0. 50% or 5000 PPM, the refinery processing not only lowered the sulfur content but also removed trace amounts of certain polar impurities. Both organo-sulfur compounds and these polar impurities were the ingredients that gave diesel fuel its needed natural lubricating qualities.
From this new low sulfur limit for all “on-road” vehicles, several laboratory testing procedures were developed in the mid 1990’s that measured the lubricity of diesel fuel. Chevron’s Technical Review of Diesel Fuels publication defines lubricity as “the ability to reduce friction between solid surfaces in relative motion, the lubrication mechanism being a combination of hydrodynamic lubrication and boundary lubrication. ” More simply stated, lubricity is that quality that prevents wear when two moving metal parts come in contact with each other. Three methods were developed which are now available for measuring fuel lubricity; namely, the Scuffing Load Ball on Cylinder Lubricity Evaluator (SLBOCLE), the High Frequency Reciprocating Wear Rig (HFRR), and the Ball on Three Seats Method (BOTS).
EPA proposed new regulations in May of this year that will further reduce sulfur for “on-road” diesel fuel to a maximum of 0. 0015% or 15 PPM. The proposed regulation is to go into effect June 1, 2006. This reduction in sulfur is fully supported by engine manufactures who contend their new exhaust catalyst systems needed to meet the enacted emission standards will not work if sulfur exceed 15 PPM. However, the proposed legislation is not supported by the refining industries and oil companies who are recommending the limit be set at 0. 0050% or 50 PPM. They explain that attempting to meet the anticipated demand for diesel fuel having sulfur at 15 PPM or less will be extremely difficult and very costly for consumers.
We first have to understand why lubricity is important for diesel fuel. There are several types of diesel fuel injection systems being used by engine manufactures which depend on fuel lubricity in varying degrees. Of all systems being used, the rotary distributor injection pump is the one most dependent on lubricity because the fuel provides 100% lubrication to the internal parts of the injection pump. As the rotary distributor injection pump is highly susceptible to boundary lubrication wear (i. e. , when heavy metal-to-metal contact occurs with the fuel providing little or no lubrication), this potential wear becomes more severe with increasing ambient temperature and increasing loading on the engine. Any significant wear will lead to under run and/or stalling annoyances, and eventually premature pump failure. The remaining other types of fuel injection systems are not as highly dependent on the fuel for lubrication and therefore, are not as sensitive to low lubricity diesel fuel, sometimes referred to as “dry diesel fuel. ”
These rotary distributor injection pumps, typically found on small to medium size engines, are widely used, and are manufactured by Stanadyne Automotive Corporation,, DENSO Corporation, Robert Bosch GmbH, and Delphi Diesel Systems. These types of fuel injection pumps are typically found in most US and foreign manufactured light duty vehicles and a wide variety of equipment systems.
Since the introduction of low sulfur diesel fuel in 1993, there has been a considerable amount of effort by the automotive industry, users, and the petroleum industry to incorporate a “lubricity requirement” in commercial diesel fuel; namely, ASTM D975. Unfortunately, this has not yet happened due to a combination of politics and other factors. However, there had been in Europe a greater awareness and acceptance for specifying a lubricity requirement. The European Union ‘s Diesel Fuel Standard EN590 now requires all low sulfur diesel fuel sold in Europe to meet a lubricity standard that uses the HFRR procedure.
In the United States, the Engine Manufacturers Association (EMA) published their “Recommended Guideline on Premium Diesel Fuel” in 1997. This document, identified as EMA FQP-1A, did include a lubricity requirement for both grades of low sulfur diesel fuel. Additionally, the World-Wide Fuel Charter published by the Alliance of Automobile Manufacturers (AAM) in January 2000 also specified a lubricity requirement for all four of their diesel fuel categories. More recently, the Diesel Fuel Injection Equipment Manufacturers (FIE) issued a “Common Position Statement on Fuel for Diesel Engines. ” in June 2000. Contained within this statement was a strong recommendation for including the same lubricity requirement as in the EN590 standard. So there has been some progress.
As low sulfur diesel fuel continues to be sold in the United States without any requirement for lubricity, there continues to exist the potential for wear problems especially in engines with the rotary distributor fuel injection pumps. The consumer is led to believe that all is well as fuel producers would not market a “low lubricity or lubricity deficient” fuel that could promote wear. That however may or may not be the case since there is “no measuring stick” presently being used. Without the enforcement of a lubricity standard, neither consumers nor fuel distributors can be certain as to whether the fuel has adequate lubricity.
As soon as the industry standard for diesel fuel D975 incorporates a lubricity standard, the potential for wear problems will become a distant memory. This standard will most certainly be needed prior to the next planned reduction of sulfur in 2006.
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