A $0.23 tax hike per gallon of gasoline is finally happening in New Jersey today, and that meant a weird form of adult trick-or-treating took place last night: people from other states — okay, pretty much just New York — rushed over the border to get their last cheap fill-up before the higher tax went into effect.

Last night, as New York Times reporters staked out a service station in Mahwah, regular gas cost about $1.90 per gallon in New Jersey.

That might seem expensive compared to where you live, but gas cost at least a quarter more in New York: today, it costs around $2.30 near Consumerist’s global headquarters in Yonkers, NY.

One graduate student living just across the border in New York state was interviewed by the times while putting $3 worth of gasoline in her Mustang. She pondered that she would probably need to get a more gas-efficient car now that she can’t go across the border to get discounted gas.

“I’m going to need a new car because of this, maybe a Prius,” she said, probably delighting a Toyota dealer somewhere with a lot full of unsold Priuses.

Not that New Jersey residents or their neighbors had a lot of time to prepare: after years of wrangling while state highway projects sat around, the state’s governor finally agreed to a gas tax increase just last month.

“When I made my financial plan for the year, I didn’t plan for this,” one motorist told the Times. She didn’t identify which state she lives in, but said that she planned to carpool more and buy fewer shoes in the coming month to make up the difference.

As Days of Cheap Gas End in New Jersey, Drivers Descend for a Last Fill-Up [New York Times]

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