Union Pacific burned 1.3 Billion gallons of diesel in 2005 at an average cost per gallon of $1.77. It should be noted that the $1.77/gallon in '05 is a 45% increase over '04's $1.22/gallon cost.
Union Pacific spent $2.4 Billion for fuel in 2005.
--hypothetically--
Additizing $2.4 Billion at a 5% increase in fuel economy throws of $119 Million annually.
Savings per week = $2.28 Million...
Savings per day = $326,923...
You may be asking where the cost of the additive is worked in the equation? For the sake of simple math, let's say it's built into the 5% increase in fuel economy as that figure is probably a conservative estimate.