Inventories

3 Months Ended

Mar. 31, 2017

Note 3—Inventories

Inventories consisted of the following:

	Millions of Dollars
	March 31		December 31
		2017	2016

Crude oil and natural gas	$	509	418
Materials and supplies		588	600
	$	1,097	1,018

Inventories valued on the last-in, first-out (LIFO) basis totaled $379 million and $269 million at March 31, 2017 and December 31, 2016, respectively. The estimated excess of current replacement cost over LIFO cost of inventories was approximately $121 million and $104 million at March 31, 2017 and December 31, 2016, respectively.