
4.	INVENTORIES

Inventories consisted of the following (in millions):



	December 31,
	2017		2016
Refinery feedstocks	$	2,427	$	2,068
Refined petroleum products and blendstocks	3,459		3,153
Ethanol feedstocks and products	242		238
Materials and supplies	256		250
Inventories	$	6,384	$	5,709

As of December 31, 2017 and 2016, the replacement cost (market value) of LIFO inventories exceeded their LIFO carrying amounts by $3.0 billion and $1.9 billion, respectively. As of December 31, 2017 and 2016, our non-LIFO inventories accounted for $1.0 billion and $641 million, respectively, of our total inventories.

During the year ended December 31, 2016, we recorded a change in our lower of cost or market inventory valuation reserve that resulted in a net benefit to our results of operations of $747 million, and we had a liquidation of LIFO inventory layers that increased cost of sales by $120 million.

During the year ended December 31, 2015, we recorded a lower of cost or market inventory valuation adjustment that resulted in a net charge to our results of operations of $790 million in order to state our inventories at market as of December 31, 2015.