Diesel Fuel Lubricity Issues Are Just Beginning

By BRETT WINBERG

This weeks edition of LubeTalk serves as a follow up to coincide with the Feb 7th Issue about low lubricity in diesel fuels.

The ASTM standard for diesel fuel, ASTM D-975 is being modified to include a specification on diesel fuel lubricity. Lubricity is determined in the fuel quality to prevent or minimizes wear in a diesel fuel system from trucks, busses and stationary equipment. Trace levels of naturally occurring polar compounds which form a protective layer on metal surfaces with in the fuel system largely provide Diesel lubricity.

A refinery hydro treating processes, which reduces the sulfur content of a diesel fuel blend, can also remove these polar compounds. As a result, most of the diesels produced by refineries to meet January 1, 2006 ultra-low sulfur diesel (ULSD) sulfur specifications will not have adequate lubricating properties to meet the new ASTM lubricity specification.

Where's The Standards?
When you take out the sulfur, you also take out lubricity and reduce antioxidancy and other valuable properties — not well for a diesel engine. The likely result: wear leading to failed injectors. And that translates into breakdowns and repair expenses. What is the standard needed from most OEM’s to determine if fuel is safe to use? This is a good question. Most OEM’s require that diesel fuels be tested using the ASTM D6078 method for lubricity and that the results be greater than 3100 PSI. Most low sulfur diesel fuels run an average of 2850 psi to 2900 psi, so some sort of additive would be required to meet OEM specification.

In diesel fuel systems, the fuel provides lubrication for the fuel pump and injectors. A fuel with poor lubricity can cause excessive wear and premature failure of these components. With reductions in fuel sulfur level, lubricity is becoming a larger concern. Many refiners are using lubricity-improver additives to restore the lubricating properties of the fuel.

Fuel Additives to Increase Lubricity
In 2004, some major U.S. finished fuel common carrier pipeline companies… announced that they would not allow the transport of diesel fuels already treated with lubricity improvers. This is due to their concerns about “trail back” of the lubricity additive into jet fuel tenders following the additive diesel, which are not allowed to contain these additives. As a result, most lubricity additive usage in the U.S. will take place at fuel terminals.

There are many fuel additives on the market that say they increase lubricity and help lubricate all the components of the fuel system, but don’t be fooled. Most fuel additives are made up of the same five constituents of diesel fuel, which in the end, really do not change any values of the diesel fuel. We recommend asking for the manufacture testing of the additive and to make sure they have tested their product using the ASTM D-6078 standard. This will give you and your equipment the assurance that improved lubricity can be achieved and that your diesel fuel is helping protect the fuel system components.

With new standards of fuel systems, we also recommend that you are using a premium fuel filter. Newer and tighter clearances require cleaner fuels with lower micron filters. The price of new injectors has risen over the years because of technology and most injector’s start out at $325.00 each. So assure your filters are of high quality and when possible, run a water separator filter to guarantee the cleanest fuel possible.

What About Testing Your Fuel Suppliers?
A good practice for all Fleet Managers would be to test the diesel fuel periodically that you are receiving from your supplier. This will assure your fuel is of ASTM D975 standards as well as reassure the cleanliness of the fuel you are burning in your equipment. Some of the recommend tests are as follows:

There are many other tests you can perform to assure the quality of your diesel fuel; however these are some of the basic tests to protect your equipment from fuel related failures.

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