"If you expect the absolute very worst in diesel fuel quality, price, and availability, you probably will not be disappointed!," exclaimed Sun Petroleum Products Technical Service Engineer Ed Boone. As light Arabian crude becomes progressively more difficult to obtain, especially in light of the ban on Iraqi & Iranian oil, imports of North Slope crude (crud) are flowing to fill the void. Today's petroleum market also contains poor quality crude extracted from previously capped domestic wells. Heavy crude oils yield up to 15% less product per barrel in the distillation range of diesel fuel than the more desirable light crude stocks, according to the Society of Automotive Engineers publications. To make matters worse, jet fuel users are now leaning toward high yield kerosene-type products, resulting in increased competition between diesel and aircraft operators for the same portion of each barrel of crude, according to Mobil's senior staff engineer Bob McCoy.
Fuel quality declines
Faced with a dwindling supply of high quality crude oil, refiners find themselves in a serious bind.
A high ranking executive with a major refiner says the quality of crude stock delivered to a given refinery can vary greatly from week to week. As a result, many refiners must either take extra time with poor quality crude or allow productivity to remain at 100% by easing up on fuel quality specifications. Most refiners now opt for the latter choice, industry sources say.
"Diesel fuel definitely is going to hell within the next six months or so." That is the opinion of United Parcel Service's federal agency relations manager Jack Allen.
Ken Van Liew, automotive service manager, Cummins Engine Company, says quasi-No.2-D diesel fuel with up to twice ASTM's maximum allowable sulfur content shows up in some areas of the country all the time.
Van Liew's concern is echoed by Bill Dysart of Union '76 Oil Company, who said coast-to-coast surveys conducted by the SAE have revealed "an extreme range of diesel fuel quality in this country today."
Unfortunately, there's little, if any, detectable change in engine power, performance or startability to tip off the unsuspecting diesel owner. "All of a sudden, the engine's 'worn out' and stops dead," Cummins officials say.
Cummins engineers suggest checking oil operating temperatures. Low oil temperatures of 160°F or less promote condensation of water which both depletes oil additives and increases sulfuric acid formation. If high humidity is characteristic of a operating area, that can make matters worse.
Symptoms of high sulfur diesel fuel combustion include a marked increase in oil consumption, crankcase blow-by with visible vapor and blue exhaust smoke. Oil analysis can be expected to show a severe decrease in alkalinity and increased concentrations of iron, chromium and sulfur products, diesel technicians report.
The effect of sulfuric acid, which accumulates in engine lubricating oil, where it quickly depletes anti-corrosion additives and proceeds to attack cylinder liners, piston rings, bearings, exhaust valve guides and other parts. High humidity makes the process even more rapid.
Determining the quality of a batch of diesel fuel can be complicated. Information from oil companies is assumed to be accurate, when often it is not. But fuel distributors, who often receive their product from a variety of suppliers, simply don't know how bad their fuel is day to day.
Sun's Ed Boone thinks "pushing suppliers for nothing but fuel in compliance with ASTM No.2-D in the future is probably fruitless and self-defeating".