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Inventories
12 Months Ended
Dec. 31, 2016
Inventory Disclosure [Abstract]  
Inventories
Inventories

Inventories at December 31 consisted of the following:
 
 
Millions of Dollars
 
2016

 
2015

 
 
 
 
Crude oil and petroleum products
$
2,883

 
3,214

Materials and supplies
267

 
263

 
$
3,150

 
3,477




Inventories valued on the LIFO basis totaled $2,772 million and $3,085 million at December 31, 2016 and 2015, respectively. The estimated excess of current replacement cost over LIFO cost of inventories amounted to approximately $3.3 billion and $1.3 billion at December 31, 2016 and 2015, respectively.

Excluding the disposition of the Whitegate Refinery, which occurred in September 2016, certain planned reductions in inventory caused liquidations of LIFO inventory values during each of the three years ended December 31, 2016. These liquidations decreased net income by approximately $68 million, $37 million and $8 million in 2016, 2015 and 2014, respectively.

In conjunction with the Whitegate Refinery disposition, the refinery’s LIFO inventory values were liquidated causing a
decrease in net income of $62 million during the year ended December 31, 2016. This LIFO liquidation impact was included in the net gain recognized on the disposition.