Ultra-Low Sulfur Fuel Lubricity Update

10 12 2009

Deere's Common Rail Fuel System Reduces Emissions While Increasing Efficiency

Everyone’s asking.
Should you use lubricity additives in this new Ultra- Low Sulfur Diesel fuel, or not?
The 2006 deadline for new Ultra-Low Sulfur Diesel-fuel standards in the US has come and gone, and with it the expected loss of fuel lubricity as well as companion standards mandating the oil industry restore lubricity with additives. So we wouldn’t have to worry about it.
Well, if only that were true. It is true that reducing sulfur from 500 ppm to 15 ppm decreased the fuel lubricity and corrosion inhibitors—and also decreased the sulfur dioxide emissions bad for all living things. It’s also true that engines and fuel systems need lubricity to prevent equipment damage and premature equipment failure. However, it is not true that the sulfur the same oil-refinery process to reduce sulfur that also removes natural fuel-lubricity agents.
Really–it’s not the sulfur. Diesel-fuel lubricity represents the ability to provide surface-contact lubrication that helps protect fuel systems. In diesel engines, rotary and distributor-type fuelinjection pumps rely on fuel as lubricant. Increasingly sophisticated diesel fuel injection equipment runs at higher operating temperatures with high injection pressures, multiple injections, &  finer tolerances—all requiring clean, lubricious fuel for performance & longevity.
All true. But the road to cleaner air emissions was paved with good intentions. Then the fuel industry lobbied for more relaxed lubricity standards, manufacturing industries compromised, & the bar got set pretty low.
Measuring lubricity is mostly based on a rather simplistic test—hardened steel ball on hardened steel plate vibrating under load while immersed in fuel to give a “wear scar” diameter on the plate. The old High-Frequency- Reciprocating-Rig test—HFRR. Smaller the scar diameter, better the results. Then ASTM specifications (American Society for Testing & Materials) set 520 µm (microns) as the maximum wear scar for diesel fuel sold in the US. Some say it’s good enough.
However, general industry agreement holds to the higher European standard of a 460-µm maximum scar. Fuel-injection equipment manufacturers got together and agreed: If over 460, their fuel-injection equipment might not meet expected lifetime performance and emissions targets.
They also said if you put in additives to increase lubricity, take care to use the right additive—but not too much of it. Bad things can happen, like internal pump-plunger and injector deposits. It’s actually come to the point where even equipment manufacturers accept biodiesel as a proven nontoxic & superior lubricity agent without the adverse effects of overdosing on other additives. But you still can’t get biodiesel in Alaska and it’s unstable, so you can’t store it or take it with you. Other than that, it’s great.
We’ve put man on the moon, yet America’s diesel engines rely on measuring a scuff mark on metal. Seems almost barbaric. Caveman tools. So, should you use additives or not? Probably. It’s like the swine-flu shot: Should you get it? Does it benefit? Are there risks? Take in all the information, ask around, make your own best decision. And rest assured we will continue following this issue & revisit it here and on the blog again.

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