Yea — I’ve lost about 1 MPG consistently. I keep mileage records on every fill up and every trip in our F-350 (for IRS purposes) and I’ve seen our mileage go down since ULSD became the norm. I do not know to what to attribute this, because I have no figures for BTU content of ULSD vs. the old #2. All I can say is that I used to see between 18 to 20 MPG on our F-350 (empty) on the highway here in Nevada, and now 18 is the high end of the mileage; we never get 20 any more.
Just over 100K miles on the 7.3L Powerstroke.
The Transition to Ultra-Low-Sulfur Diesel Fuel: Effects on Prices and Supply
http://www.eia.doe.gov/oiaf/servicerpt/ulsd/chapter2.html
2. Efficiency and Cost Impacts of Emission Control Technologies
Efficiency Losses
New vehicle fuel efficiency is reduced slightly in the 4% Efficiency Loss case, but the impact on stock efficiency is marginal because the number of new vehicles expected to enter the market is small relative to the total number of vehicles on the road. Fuel expenditures for heavy trucks are projected to be $1.9 billion higher in 2007 in the 4% Efficiency Loss case than in the reference case, and the difference grows to $2.9 billion in 2011 (Table 1), an increase of $410 in average fuel expenditures per truck. Cumulative fuel expenditures from 2007 to 2015 are projected to be $17.6 billion higher in the Regulation case than in the reference case and an additional $3.0 billion higher in the 4% Efficiency Loss case. The projected cumulative increase in energy use in the 4% Efficiency Loss case is approximately 80 trillion British thermal units (Btu).
Appendix D: Short-Term Analysis of Refinery Costs and Supply
http://www.eia.doe.gov/oiaf/servicerpt/ulsd/appendix_d.html
Hydrotreater Yields and Energy Content: The volume and weight percent yields of ULSD produced by the distillate hydrotreater can vary considerably, depending on the fraction of cracked stocks in the feed and the level of aromatics saturation. An average yield and energy content were estimated for this study, based on the Criterion data in a June 2000 study by the National Petroleum Council.167 The yield of hydrotreater product in the distillate boiling range was assumed to be 98 percent by weight, and the API gravity was assumed to increase by 2 numbers, which means that the volume yield was 99.2 percent. There was also a small increase in the Btu content of the product on a weight basis (98.2 percent of the feed energy content in 98.0 weight percent of the feed). The energy content declines on a volume basis, because the heat content of the product is 0.989 times the heat content of the feed on a volume basis.
ABCs of ULSD
http://fleetowner.com/mag/fleet_abcs_ulsd/
Energy content
In general, 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). A 1% reduction is expected, which may affect mpg.