LOVELOCK - Is the diesel fuel you use today the same as your grandfather used 50 years ago? Is all diesel fuel created equal? Why does diesel fuel cost more than gasoline?
Historically speaking, diesel fuel was developed in the mid-1920s to meet the growing demands of the newly introduced diesel engines and vehicles. Diesel fuel was classified as medium-weight oil in comparison to gasoline being a lightweight oil.
Diesel can be classified in several ways. The first way is by its sulfur content. The next difference in diesel fuels can be in it being an on-road or off-road fuel. The last way is by its volatility.
When diesel fuel was introduced, it was a very high-sulfur fuel and was primarily designed for the early diesel fuel systems. Higher sulfur content resulted in greater lubricating value but also in higher emissions or particulate matter.
Now with the current demand for higher emissions standards, diesel fuel has changed. In 2006, the Environmental Protection Agency (EPA) mandated that all diesel fuels should be low-sulfur. Low-sulfur would be designated by 500 ppm (parts per million) units of sulfur.
By the end of 2010, EPA again mandated that all diesel fuel intended for use on the road should be ultra-low-sulfur diesel fuel. Ultra-low-sulfur diesel fuel or ULSD was designated by 15 ppm units of sulfur. Off-road fuel could still be low-sulfur fuel. Then again in 2011, all diesel fuels produced in the U.S. were mandated to be ULSD, whether they were intended for on road or off-road use. Now diesel fuel contains as much as 100 times less sulfur content than it did 10 years ago. Although it is a much cleaner fuel, this reduction in emissions does come with a cost.
Ultra Low Sulfur Diesel contains less heat energy per gallon than high-sulfur fuels due to the refining process. This can constitute for a lack in performance when comparing the two variations of diesel fuel. Another side effect of the lack of sulfur in the fuel is that many of our older fuel injection systems suffer.
Less sulfur indirectly means less lubricating value and less lubricating value equals older fuel systems that fail a lot sooner than intended. The vast majority of the older fuel systems were designed for high-sulfur fuels - not ULSD. So, for your older diesel equipment or vehicles, it would pay to put a diesel lubricant additive in with each tank of diesel.
Many diesel consumers believed that the non-taxed off-road fuel was still high-sulfur fuel and only the on-road fuel was ULSD. The only difference currently in the two fuels is the red dye used to distinguish the taxed fuel from the non-taxed fuel. Other than that, the two fuels are identical in their chemistry and sulfur content.
Are there differences in diesel fuel from one pumping station to the next or from one time of year to the next? The answer is, yes. This brings us to our next point on fuel - volatility.
Have you ever put a winterized blend of diesel fuel in your equipment or diesel vehicle during the winter months? Winterized fuels can be a blend of No. 1 diesel and No. 2 diesel fuel. No. 1 diesel has a higher volatility than the No. 2 diesel. This means that not only can it atomize better or turn from liquid to vapor easier, but it also has a lower gelling point. A lower gelling point aids fuel to keep it from gelling or waxing in colder temperatures. This is great for keeping your diesel vehicle running in the winter.
Winterized fuels are great for cold temperatures, but they do actually have one downside. No. 1 diesel fuel has a lower cetane rating than No. 2 diesel fuel. Cetane rating refers to the ability of the fuel to combust - in other words, the combustion quality of the fuel.
Cetane ratings in diesel fuel can be compared to octane ratings in gasoline fuel - the higher the number, the better. Most No. 2 diesel has a cetane rating of anywhere from 50 to 55 points.
Most No. 1 diesel fuels have 40 to 50 cetane points. Simply put, there is less heat energy in one gallon of No. 1 diesel fuel than there is in one gallon of No. 2 diesel fuel. This will explain why your diesel pickup gets 18 miles per gallon in the summer and when winter hits it only gets 15 mpg. It will also explain why your diesel equipment has a harder time starting in the winter months. One alternative to winterized fuel is to add a winterizing additive, which will not lower the cetane levels.
So, why does diesel fuel cost more than gasoline? The price of diesel traditionally rises during colder months as demand for heating oil rises, which is refined in much the same way. Also, because of recent changes in fuel emission regulations, additional refining is required to remove the sulfur, which contributes to a sometimes higher cost. Other reasons for higher-priced diesel include the shutdown of some refineries in the Gulf of Mexico and diversion of mass refining capacity to gasoline production all contribute to higher priced diesel fuel.
So, is the diesel fuel you use today the same as your grandfather used 50 years ago? No, not by a long shot.
Source: Levi Perkins, instructor, Diesel Technology Program, College of Southern Idaho
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