I went back to TDR Issue 36 (pages 24-28), which exposed the premium diesel designation as a justification to charge more for something that is better, but not necessarily better in ways that are important.At the heart of the article is the research of Amalgamated, Inc, a supplier of bulk fuel additives to terminals and distributors. Their investigation showed that the standard for premium diesel was so loose that fuels could legitimately be labeled premium and still burn no better (or even worse) in the vehicle than non-premium fuel.In particular, fuels with no improvements in energy content, cetane number, lubricity or low temperature operability could all legally and legitimately carry the premium designation!

As Issue 36 pointed out, the National Council of Weights and Measures definition allows a fuel to be labeled "premium" if it meets two out of the following five criteria:

- Cetane number:47 or greater
- Injector detergency:10 maximum, using Cummins L-10 test
- Thermal stability:80% pad reflectance
- Low Temperature operability:Low temperature flow test, LTFT, or cloud point test results within the 10th percentile of the ASTM spec.
- Energy content:138,700 BTU minimum

In the fall of 1999, TDR Issue 26 (page 15) teased us with the possibility that ASTM was considering a new, more rigorous set of standards for premium diesel. In the follow-up Issue 36 (summer 2002) article those hopes were dashed with the news that nothing had been implemented and that we were still stuck with the two out of five definition.The Issue 36 article ended with the conclusion that premium diesel was not worth the price and recommended that as consumers we should insist on a written guarantee that fuel labeled, "premium diesel" should meet all of the following criteria:

- Cetane number:50 or greater
- Injector detergency:10 maximum , using Cummins L-10 test
- Thermal stability:exceeds 80% reflectance
- Cold Filter Plugging Point, CFPP:10 degrees F below the lowest expected local ambient temperature
- Contains anti-icing agents to prevent fuel lines from freezing
- Fuel is pure #2 diesel, not highly blended with #1
- Lubricity: meets 3300 grams, using SLBOCCLE test
- Contains rust and corrosion inhibitors for a NACE 1-A rating

Pretty impressive list!Too bad it never made it on the agenda of ASTM or NCWM.

January 2004 Update

It turns out that the NCWM did adopt a new definition of premium diesel replacing the two-of-five cafeteria-style definition. This definition became effective January 2004.No labels are required on the retail pumps for fuel meeting this definition.Now it became clear why the fuel that I was so cautious about in my January 2005 storyline was not labeled.It was manufactured under the new definition which I was able to verify with the supplier.Here is the new definition:

Diesel fuels identified on retail dispensers, bills of lading, invoices, shipping papers, or other documentation with terms such as premium, super, supreme, plus, or premier, must conform to the following requirements:

- Cetane Number – A minimum Cetane number of 47.0 as determined by ASTM Standard Test Method D613
- Thermal Stability – A minimum reflectance measurement of 80% per ASTM D6468
- Low Temperature Operability – A cold flow performance measurement which meets the ASTM D975 tenth percentile minimum
- Lubricity – A maximum wear scar diameter of 520 microns per ASTM D6079.If a single test of more than 560 microns is determined, a second test shall be conducted.If the average of the two tests is more than 560 microns, the sample does not conform to the requirement.

The 2004 criteria provides us with a far better definition for premium diesel fuel.Finally, a cetane number specification higher than 40!However, you should be aware that the injector detergency test has been dropped, the minimum energy content requirement has been dropped, and a new specification for lubricity is described.

The lubricity specification is interesting.The NCWM definition of premium diesel requires that the average of two sample tests must be lower than 560 microns.But, how is that better than ASTM D975 which specifies 520 microns?The dilemma is resolved by noting that the NCWM definition of premium diesel, adopted in January 2004, came at a time when ASTM D975 contained no lubricity spec.It was not until one year later (January, 2005) that the current lubricity spec of 520 microns appeared in D975.

However, the 2004 NCWM definition for premium diesel lubricity does provide a benefit over the 2005 ASTM D975 specification.The NCWM definition of premium diesel essentially restricts the measurement error and guarantees that the fuel will meet a slightly higher standard but with greater confidence and a narrower acceptance criterion.Considerable room for improvement exists for NCWM and ASTM to converge on a specification with greater precision, and to clarify whether or not premium diesel should have a superior lubricity specification or not.

Will Our Hopes Again Be Dashed?

Room for improvement aside, the 2004 NCWM definition of premium diesel is a great step forward.For the first time, we have a definition that defines a fuel with a predictable and meaningful benefit to the consumer.

Now for the bad news:From my report on fuels in Issue 54 you will remember that it is up to the individual states to decide if, and to what degree, they will adopt the lubricity specifications that are a part of ASTM D975 in their specifications for ULSD.Also, only half of the states have adopted the latest D975.The situation is even worse for the NCWM definition of premium diesel.Marilyn Herman of Herman and Associates informs me that only a very small handful of states have adopted the definition of premium diesel, and most states do not have any definition of premium diesel at all.

At least we can say there is progress.

From state regulatory standpoint the industry is largely unchanged. Therefore, without research there no way of knowing what definition (if any) of premium diesel is used at the retail pump in your area.Note, however, that fuel suppliers do have reputations to protect and may follow the new NCWM definition even without local state enforcement.You may find, as I did, that the good stuff is available in your area.Contact your local state fuel quality or Weights and Measures agency to find out what regulations are in place, and contact the fuel suppliers represented in your area to verify what is actually sold.

ASTM International
www.astm.org