index. (viii) CAFE fuel saved adjustment For purposes of clause (iv), the CAFE fuel saved adjustment for a calendar year is the percentage (if any) by which annual motor fuel use is reduced by the estimated CAFE fuel saved for that calendar year from the annual motor fuel use for the prior calendar year. (ix) Estimated CAFE fuel saved The term estimated CAFE fuel saved for a calendar year means— (I) In the case of the 18.3 cents rate in subparagraph (A)(i), the combined gasoline fuel saved estimates issued by the National Highway Traffic Safety Administration and the Environmental Protection Agency for passenger automobiles and light trucks published in the Federal Register on May 7, 2010, and October 15, 2012, and for medium and heavy-duty engines and vehicles published in the Federal Register on September 15, 2011, and October 25, 2016, as part of final rules to implement corporate average fuel economy standards, and such successor estimates included in successor rules. (II) In the case of the 24.3 cents rate in subparagraph (A)(iii) and the 19.7 cents rate in subparagraph (D), the combined diesel fuel saved estimates issued by the National Highway Traffic Safety Administration and the Environmental Protection Agency for medium and heavy-duty engines and vehicles published in the Federal Register on September 15, 2011, and October 25, 2016, as part of final rules to implement corporate average fuel economy standards, and such successor estimates included in successor rules. (x) Annual motor fuel use The term annual motor fuel use means— (I) In the case of the 18.3 cents rate in subparagraph (A)(i), the total number of gallons of gasoline used in a calendar year in highway use, as published by the Federal Highway Administration as part of its annual motor fuel data survey. (II) In the case of the 24.3 cents rate in subparagraph (A)(iii) and the 19.7 cents rate in subparagraph (D), the total number of gallons of diesel used in a calendar year in highway use, as published by the Federal Highway Administration as