This report discusses the Strategic Petroleum Reserve (SPR) in the Energy Policy and Conservation Act, which was authorized to help prevent a repetition of the economic dislocation caused by the 1973-1974 Arab oil embargo. The Government Accountability Office recently observed that the proportion of crude oil grades in the SPR has been growing less compatible with the heavier grades of crude oil that U.S. refineries have been upgrading to handle. This finding has raised questions about the SPR's effectiveness during a long-term oil disruption involving heavy oil.