In case you were wondering how they got that magic number 84,000 gallons, it probably comes from 2,000 barrels (http://www.eia.gov/tools/faqs/faq.cfm?id=24&t=10

In case you were wondering how they got that magic number 84,000 gallons, it probably comes from 2,000 barrels (http://www.eia.gov/tools/faqs/faq.cfm?id=24&t=10 http://www.eia.gov/tools/faqs/faq.cfm?id=24&t=10), so it's a rather rough estimation (one significant digit, not two). EDIT: 2,000 barrels instead of 20,000.