All else equal, this would increase gasoline prices, which in most of the country have averaged $3 per gallon for the past year amid historically low levels of petroleum inventories (see chart). But Trump wants lower gasoline prices, which is why if the oil tariffs come at all, they will likely start slowly.

Oil prices rose on Friday as markets weighed the threat of tariffs by U.S. President Donald Trump on Mexico and Canada, the two largest crude exporters to the U.S., that could take effect this weekend.