levels during 2008 , an indication that efforts to improve network operations translated into better customer service . 2022 fuel prices 2013 crude oil prices increased at a steady rate through the first seven months of 2008 , closing at a record high of $ 145.29 a barrel in early july . as the economy worsened during the third and fourth quarters , fuel prices dropped dramatically , hitting $ 33.87 per barrel in december , a near five-year low . despite these price declines toward the end of the year , our 2008 average fuel price increased by 39% ( 39 % ) and added $ 1.1 billion of operating expenses compared to 2007 . our fuel surcharge programs helped offset the impact of higher fuel prices . in addition , we reduced our consumption rate by 4% ( 4 % ) , saving approximately 58 million gallons of fuel during the year . the use of newer , more fuel efficient locomotives ; our fuel conservation programs ; improved network operations ; and a shift in commodity mix , primarily due to growth in bulk shipments , contributed to the improvement . 2022 free cash flow 2013 cash generated by operating activities totaled a record $ 4.1 billion , yielding free cash flow of $ 825 million in 2008 . free cash flow is defined as cash provided by operating activities , less cash used in investing activities and dividends paid . free cash flow is not considered a financial measure under accounting principles generally accepted in the united states ( gaap ) by sec regulation g and item 10 of sec regulation s-k . we believe free cash flow is important in evaluating our financial performance and measures our ability to generate cash without additional external financings . free cash flow should be considered in addition to , rather than as a substitute for , cash provided by operating activities . the following table reconciles cash provided by operating activities ( gaap measure ) to free cash flow ( non-gaap measure ) : millions of dollars 2008 2007 2006 .
what was the percentage change in free cash flow from 2006 to 2007?
2009 outlook 2022 safety 2013 operating a safe railroad benefits our employees , our customers , our shareholders , and the public . we will continue using a multi-faceted approach to safety , utilizing technology , risk assessment , quality control , and training and engaging our employees . we plan to continue implementation of total safety culture ( tsc ) throughout our operations . tsc , an employee-focused initiative that has helped improve safety , is a process designed to establish , maintain , and promote safety among co-workers . with respect to public safety , we will continue our efforts to maintain , upgrade , and close crossings , install video cameras on locomotives , and educate the public about crossing safety through various railroad and industry programs , along with other activities . 2022 transportation plan 2013 in 2009 , we will continue to evaluate traffic flows and network logistic patterns to identify additional opportunities to simplify operations and improve network efficiency and asset utilization . we plan to maintain adequate manpower and locomotives , and improve productivity using industrial engineering techniques . 2022 fuel prices 2013 on average , we expect fuel prices to decrease substantially from the average price we paid in 2008 . however , due to economic uncertainty , other global pressures , and weather incidents , fuel prices again could be volatile during the year . to reduce the impact of fuel price on earnings , we .