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Inventories
 12 Months Ended
Dec. 31, 2022
Inventory Disclosure [Abstract]  
Inventories Inventories
December 31,
(Millions of dollars)20222021
Crude oil $3,047 $2,639 
Refined products4,748 4,460 
Materials and supplies1,032 956 
Total$8,827 $8,055 
The LIFO method accounted for 88 percent of total inventory value at both December 31, 2022 and 2021. Current acquisition costs were estimated to exceed the LIFO inventory value by $3.72 billion as of December 31, 2022. There was $2.84 billion excess of replacement or current cost over our stated LIFO cost at December 31, 2021.
The cost of inventories of crude oil and refined products is determined primarily under the LIFO method.