Let's count the ways that using diesel to run frack jobs causes problems. First, emissions diesel engines, especially from the many older ones in the field, can be a significant source of pollution. Second, about 40% of the oil used to make the diesel is imported or is foreign oil. Third, the diesel is expensive, currently costing about $3.60 per gallon.
That's three strikes against using diesel, and diesel is increasingly striking out. See Marc Levy's story that documents the switch to natural gas to reduce the amount of diesel used for fracking.
Levy focuses on PGE and Universal Well Services that are operating in Pennsylvania and reports that PGE will cut its annual diesel use by 750,000 gallons by switching to natural gas. By my calculations, PGE will save about $2.25 million per year by doing so.
PGE's executives believe that the switch to natural gas for fracking will be quick and widespread in the industry. That would be welcome, since the gas industry consumes huge amounts of diesel currently to produce natural gas and some of that is running old, dirty engines.