Yes and they seem good at this, too. News reports are that they started stockpiling in January at the latest in prevision of a conflict in Iran that did start right at the end of February.

They started stockpiling in 2024. The estimate is that they had 1.4 billion barrels by the time the Iran war started, and they're down to 1.2 billion now. (Nobody knows for sure, though.) Meanwhile the US has 304 million barrels left in our reserves, but there's a (disputed) operational minimum around 225 million, where draw slows down and the caverns start to suffer damage. (That's about 90 days at current draw rates. Also, this is a loan program, where oil needs to be "repaid" with interest starting in November, so that's going to affect prices too.)