If you are looking to improve ULSD lubricity, studies have shown that a low percentage of biodiesel regains the lost lubricity. "Biodiesel can increase fuel lubricity to diesel fuels at blend levels as low as 1%."
http://www.afdc.energy.gov/fuels/bio..._benefits.html
Also, " Removing the sulfur from diesel fuel
reduces the lubricity of the fuel, which could cause
concern for the operator of diesel engines. Biodiesel
is an excellent lubricant for the fuel injection system.
The addition of as little as 1 percent to 2 percent
(B1 or B2) would give diesel fuel more lubrication
than previously accomplished with higher sulfur
content diesel fuel."
http://www.agmachinery.okstate.edu/e...%20Engines.pdf
Maybe less expensive and better for the environment?