Miriam Mandelman has been trying not to run any extra errands.

She hasn't been going shopping for herself, or treating herself. It's not worth it, when there are bills to pay and day-to-day costs — in particular, gas costs — that seem out of control.

"It's very difficult because I have two very small children and I work in a public school, so my salary is pretty fixed," the 46-year-old said after she pulled up to the Amoco on Route 17 in Ramsey, New Jersey, on Thursday. "I have to drive my daughter to school and my son to therapies. I'm trying not to get gas as often as possible, waiting until I'm almost in the red, so that way I can wait and see if the prices will be dropping anytime soon."

And that day, prices had indeed dropped: Gas was only $3.99. Only.

It wasn't long ago that $4 gas seemed like highway robbery. But with factors including the Russia-Ukraine war sending prices over $5 in recent months, and prices in Manhattan still averaging more than $4.60 over the last several days, $4 was a bargain.

The Amoco was one of a few New Jersey stations — most of them in the Mahwah and Ramsey area, in northern Bergen County — to dip below $4 this week. Gasbuddy.com's tracking showed nine of the top 10 cheapest gas prices in the state at $3.99 as of late Friday afternoon.

Average gas prices in New Jersey reached just over $5 in early and mid-June, according to Gasbuddy.com. They've been dropping ever since, fairly closely following national trends. The average in the Garden State was $4.47 on Friday, and $4.38 nationwide.

Sal Risalvato, executive director of the New Jersey Gasoline-Convenience-Automotive Association, told Gothamist there are a few factors in play. A few gas stations have benefited from a significant decrease in wholesale costs. But mostly, he said, it's that, people are buying less gas.

"The best remedy for high gas prices is high gas prices. As people start to change their driving habits and gasoline volume decreases, it puts downward pressure on the price," he said.

But what goes down could go up. If people become more comfortable with gas prices, and start hitting the road again, expect prices to rise, Risalvato said.

Patrick De Haan, head of petroleum analysis at Gasbuddy.com, was cautiously optimistic a downward trend could continue for the next few weeks. But he said any one of a number of factors could send prices rising. If economic indicators start looking up, so will gas prices. And if a hurricane or other natural disaster hits refinery production — and this is hurricane season — prices could spike.

"Supply is barely adequate to meet demand," he said. "But if the economy does slow down, that would give us a little bit more breathing room."

Scott Royster, 32, filled up his tank at the Gulf on Franklin Turnpike in Mahway Thursday. The $4.05 price there was the best he'd seen so far.

"Before the spike went up, I was probably spending maybe around $25 to fill up my tanks," Royster said. "Now it’s $50, $55...I don’t actually go out of my way to fill up gas, but this is the best gas I’ve seen in a long time."

Brianna Stoohs, 22, came to the Gulf as well that day. She was on a trip to her alma mater in South Carolina, 10 hours away. Without her parents' help, she said, she couldn't have afforded the gas for the trip. It felt "a little shameful," she said, but she was grateful for the support.

That same day, Gina Mazzariello, 31, caught wind of the $3.99 price and rushed out to the Amoco on a virtually empty tank. When she got there, the pump ran out after 5 cents worth of gas.

"I’m feeling a little annoyed," she said. " I just drove down (Route) 17 to come here and how I’m going to have to lap back — and I don’t have a lot of gas."