Is ULSF as Safe for Diesel Engines as they say? - By: Premo Oilman

Loss of Energy (Mileage)
The processing required to reduce sulfur to 15 ppm also reduces the aromatics content and density of diesel fuel, resulting in a reduction in energy content (BTU/gal). Chevron tells you to expected a reduction in energy content of 1% and may affect fuel mileage.
Recent calls from disgruntled long-haul diesel drivers have stated much higher losses in mileage. Most diesel owners are reporting about 8-10%. Tim Riley, a VP of Operations at Exclusive Nationwide, an expedited delivery service states, “all of my 31 drivers have lost 2 miles/gallon in highway driving with ULSF."

Loss of Lubricity
Lubricity is a measure of the fuel's ability to lubricate and protect the various parts of the engine's fuel injection system from wear. Althrough sulfur is not a lubricant, the process used to reduce the sulfur also reduces the fuel's lubricating properties. The severe hydrotreating removes naturally-occurring lubricity agents in diesel fuel. Fuel is the only conduit the injectors & fuel pump surfaces have for lubrication. The loss of lubricity in ULSF will expose metal surfaces in the fuel system and engine top-end to greater friction and wear. Exclusive Nationwide told us that last month alone, 5 of their diesel drivers had an average cost of $3000.00 in injector work done to their trucks. None of his drivers use a high quality diesel additive. Dealerships we spoke with say that since the fuel change, injector repairs have increased.

Loss of Corrosion Resistance
Equipment Manufacturers Institute (EMI) reports that ULSF can lose natural antioxidants that help prevent the fuel from forming gums & sludges. Antioxidant properties are vital in modern fuel systems that are exposed to higher operating temperatures. ULSF becomes less stable with the additional sulfur processing. "Fuel stability" is a term used to describe fuel's resistance to the formation of gums and insoluble oxidation products. Fuels with poor oxidation stability contain insoluble particles that can plug fuel filters. This may lead to decreased engine performance or engine stalling from fuel starvation. Oxidation is thought to cause the premature deterioration of older seal material and cause leaking of injectors when the sulfur content in diesel fuel is drastically lowered.

A Chevron bulletin tells us that a small number of vehicles may require preventative maintenance in the form of upgrading certain engine and fuel system seals that may not perform well in the transition to the new fuel and could leak. Studies of test fleets have indicated that fuel system leaks are not exclusive to a particular engine type, fuel type or geographic region.

SUMMARY
The additional hydrotreating of diesel fuel to get 15 ppm affects the energy of the fuel, its lubricity, and its corrosion resistance properties. Big oil companies will tell you they treat the fuel to meet lubricity standards, but the only monitoring currently is to determine if the diesel fuel is <15 ppm sulfur. At best, most fuel suppliers use the lowest additive concentration (LAC), which does not always meet the minimum lubricity standards.
ULSF is here to stay and the only defense is a high quality diesel fuel additive. A good additive provides injector & fuel pump lubrication, anticorrosion & seal protection, and restores fuel quality for improved mileage.

Articles used:
"ULSD could trigger other problems besides lubricity" by Jack Peckham
Chevron "New S15 (Ultra Low Sulfur Diesel - ULSD) Regulations"

What affect does the new ULSF have on a diesel engine? The results are not as minimal as you are lead to believe. The rigorous hydrotreating of diesel fuel to get 15 ppm affects the fuel in several important ways.

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