Tensions with Iran have been pushing oil prices up over $100 a barrel and it won't take a full-blown war to send them much higher, possibly to $140 a barrel, says Mike Breard, an oil and gas analyst at Hodges Capital in Dallas.

Oil futures are skyrocketing thanks to Iranian tension, with U.S. crude futures hovering over $102 a barrel and Brent futures, which drive European markets, at around $118.

Brent and U.S. futures historically trade at a much narrower spread, and many analysts expect that gap to narrow as the U.S. economy improves.

The West has been slapping fresh sanctions on a defiant and nuclear-ambitious Iran, which is taking steps to cut off oil supply and even threatened to close down the Strait of Hormuz, a key waterway for the world's oil industry.

With nerves on edge and the Strait of Hormuz crawling with edgy warships and oil tankers, a messy encounter would be enough to send oil skyrocketing.

"All that has to happen is for a tanker to hit a mine and the prices will be jumping," says Breard, according to the Christian Science Monitor.

"A lot of people are afraid of oil rising to $140 a barrel."

Tensions with Iran and refinery closures along the U.S. east coast are pushing gasoline prices to record highs so early in the year, and many worry that as spring and summer approach, when gasoline prices are at their highest, the U.S. could see prices well above $4 a gallon.

"We are on track for a very expensive summer," says Sander Cohan, a gasoline-market analyst and principal at Energy Security Analysis in Wakefield, Mass., the Christian Science Monitor adds.

Gasoline prices are averaging $3.53 a gallon, up 25 cents since Jan. 1, according to the Associated Press.

Expect prices to hit a record $4.25 a gallon by April.

"You're going to see a lot more staycations this year," says Michael Lynch, president of Strategic Energy & Economic Research, the AP adds.

"When the price gets anywhere near $4, you really see people react."