Miniscule benefit
According to the first reputable-looking website with actual numbers I stumbled on,
http://www.nationmaster.com/graph/ene_oil_con-energy-oil-consumption
Daily US oil consumption in 2007 (probably close enough for government work) was 20,680,000 bbl/day. At 42 gal/bbl, that works out to roughly 869 million gal/day.
The United States would burn through two hundred million gallons in about 6 hours.
