Gas prices always soar in the springtime.

Northerners venture out of their houses more as milder weather arrives, and the market anticipates higher consumption for summer vacation trips.

This year, analysts say, prices could cross the psychologically significant $4-per-gallon mark, adding as much as 60 cents per gallon to the current national average.

There are several reasons, according to USA Today. The economy is improving, jobless rates are falling, and threats by Iran to close the Strait of Hormuz continue to make global oil markets nervous.

According to projections by GasBuddy.com, which tracks gas price trends state by state, the average national price per gallon will likely peak around Memorial Day at about $4.

That means that prices in the most expensive (which translates to most highly-taxed) of the 48 states could hit levels as high as $4.60 a gallon.

Want proof? Last May, gasoline spiked to an average price of $4 per gallon across all U.S. markets. (Then it fell below $3.50 early last autumn.)

Four dollars a gallon seems to be the psychological limit that causes people to change their behavior, either driving less or thinking harder about vehicles with higher gas mileage.

Gas pump with dollars

Gas pump with dollars

If the current fragile economic recovery continues and strengthens, sooner or later, many households will have to replace their vehicles. The average car on U.S. roads is now more than 10 years old--the highest average age since World War II.

And with required corporate average fuel economy rising every year from now through 2016--and new standards reaching toward 54.5 mpg by 2025 out for public comment--new vehicles are likely to deliver notably lower fuel consumption.

The rising average fuel economy of cars on the road, as older cars are replaced with newer ones, is one of the reasons why--contrary to public belief--U.S. consumption of gasoline peaked in 2006.

It's been falling ever since.

But the cash you lay out for it? That's a different  story altogether.

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