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Driver Lifestyles

Diesel...Lifeblood of the Nation

By Gary Addis
Posted Oct 7th 2002 2:14PM


Here in America-- the land of plenty-- we ignore the well till we need a drink of water. Likewise, during summer and spring truckers top their tanks with fuel once a day, then completely forget them.

But when the mercury's hovering around zero (ten months of the year in some parts of the country) water freezes in unprotected pipes, and untreated diesel thickens into waxy sludge.

Diesel is a highly efficient source of energy. The BTU rating of diesel surpasses that of all other carbon-based liquids, including gasoline. It ain't perfect, though-- no fuel is.

All petroleum distillates contain paraffin wax: that's the reason they feel “oily” when rubbed between the fingertips. This wax protects an engine's moving parts from friction. If it could be removed completely, no refinery would...some other lubricant would have to be added.

So paraffin isn't necessarily the evil contaminant many drivers think it is. I added a qualifier to that statement for a reason, however. Although the paraffin content of diesel fuel keeps hard-working truck engines from grinding their cylinders into dust, as the temperature drops the wax begins to crystallize, forming globs of gelatinous muck that clogs filters and fuel lines.

As the fuel in his tanks begins to cloud, the driver may notice a loss of power; he may have to apply a lot more pedal to maintain his speed. At this point a gallon or so of commercial additive poured into each tank may save his day, but if he ignores the problem and the temperature continues to drop, pretty soon the starved engine begins to lug. A few minutes or even seconds later, without any additional warning signs, it quits.

Looking out for number one.

It's said that God looks after kids and fools. Truckstop operators do all they can to help. They buy fuel that's specially blended for conditions prevalent in their part of the country.

The Maintenance Council of the ATA recommends that #2 diesel be blended to a fuel cloud point of five to ten degrees and a pour point at least twenty-five degrees below the expected ambient temperature. But Mother Nature doesn't always cooperate; a freezing Arctic wind can blow down from the north quite unexpectedly. And do keep in mind that fuel bought in Miami isn't formulated for a frigid waltz across Ohio.

So protect yourself: buy diesel regionally. If you're expecting subzero temperatures where you're going, and your fleet permits you to, consider topping your tanks with #1 diesel, a special winter blend of diesel and kerosene.

Since kerosene contains less paraffin, it lowers the fuel's pour point. Be aware, though, that your fuel mileage will suffer, especially in mountainous regions. A common misconception of inexperienced drivers is that kerosene-blended diesel is more powerful. To the contrary.

According to one mechanic, #1 diesel does contain fewer contaminants. But judging by its BTU rating, it also burns cooler, and in a mechanically sound truck engine, combustion heat translates directly into hill-climbing power.

Fuel Facts

Fuel analysis has become a very important part of all fleet maintenance and purchasing functions. By Federal mandate and state law, diesel fuel must meet certain minimums, but the standards still permit a wide variance in quality from producer to producer. If you ask, most reputable truckstops will gladly show you the specs on the grades of fuel they sell.

Here are a few definitions to help you understand the report:

· BTU-- acronym for British Thermal Unit, the official measure of a fuel's energy content. Theoretically at least, one BTU will raise the temperature of one pound of water by one degree Fahrenheit. So the higher this figure is, the better. Most diesel sold in the U.S. will have a minimum BTU rating of 130,000 per gallon of fuel.

· Cloud Point-- the temperature at which the diesel fuel begins to crystallize. At this temperature the diesel will still flow, but the wax may already be slowly clogging your fuel lines and filters. Chemical additives alone won't lower your fuel's cloud point, but they may reduce the size of the wax or ice crystals that are being formed.

· Cetane Rating-- cetane rating is a measure of the ignition quality of the fuel. The higher a fuel's cetane value, the easier the engine will crank in frigid weather. A cetane rating of 40 is considered the absolute rock-bottom.

· API Gravity-- a scale developed by the American Petroleum Institute to compare the density of petroleum products. The higher the value, the less dense the fluid. Water has an API of 10. Products heavier than water have an API of less than 10. Number 2 diesel has an API between 30 and 36; Kerosene has an API of 40 to 45.

· Pour Point-- the pour point of #2 diesel is about five degrees above the temperature at which it solidifies. A truckstop's diesel pour point should be at least twenty degrees below the lowest temperature expected in the region.

· Viscosity-- a measure of the fuel's thickness, it will vary according to the fuel's internal temperature. High viscosity requires high injection pressure, which places undue strain on injector components. Low viscosity may lead to leakage from injection pump and individual injectors. Additionally, the thinner the fuel, the less efficiently it lubricates. Target viscosity, at a fuel temperature of 100°, is 34 to 36.

· ASTM Testing-- the results of miscellaneous ASTM tests may be included in the truckstop's fuel report, including:

ITEM                         ACCEPTABLE RANGE

Carbon Residue                   0.35% max.

Water & Sediment               0.05% max.

Ash Content                      0.01% max.

Sulfur Weight                     0.50% max.

Flash Point                         52 min.

what to look for in a fuel additive

· Cetane boosters--alkyl nitrates, peroxides and/or nitro-compounds. These chemicals increase a fuel's oxidation, effectively improving the fuel's combustibility for cold weather starting. Look for concentrations up to .25% by weight.

· Cloud Point Depressants-- as the name implies, they lower the fuel's cloud point. It'd take several bottles of additive to appreciably alter two hundred gallons of fuel, however. But the 2 or 3° temperature margin they do provide may be just enough to see you safely home.

·  Pour Point Depressants -- alter the size of the fuel's paraffin crystals as it starts to gel, thereby helping to maintain fuel flow.

If your tanks are filled with fuel that was formulated for the Tropics, you can't expect to drive through a North Dakota blizzard without your fuel lines becoming clogged with great globs of gelatinous wax. In other words, you have to buy quality fuel that has been blended for local weather conditions.

Fuel additives can't perform miracles-- they shouldn't be expected to. They can, though, provide you with a 5° or 10° cushion.

But shop carefully. Especially during the winter months, you get what you pay for...the cheapest price at the pump is not necessarily the best bargain.


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