CHICAGO (CBS) – It’s hard to know when it’s the right time to fill up on gas.

Triple A reports the average price in Chicago is now $4.40 a gallon – one cent less than it was yesterday and 4 cents less than it was last week.

But beware of the summer-blend that kicks in next week. It could force prices up by 5 cents per gallon.

CBS 2’s Dorothy Tucker explains why maybe that’s not a bad thing.

While none of us look forward to the increased price of summer blend gas, we do like the increase in gas mileage.

“I’m a limousine driver, so I get about 20 miles a gallon and maybe a little more with the summer blend,” Jim Guthrie says.

Joe Betancourt says the summer blend can stretch mileage as much as three miles per gallon. So, if you usually get 450 miles to a tank of gas, you could travel another 80 miles before filling up again.

“Rush hour really, really works against you,” he says. “The quicker you can get your vehicle in a higher gear … the better the gas mileage.”

Other tips: Don’t gun the engine out of every light. On the highway, maintain 55 mph; you can save three miles per gallon. Skip warming up the engine in the morning. Avoid idling.

“Shut the car off. It really makes a difference,” he says.

That difference adds up. Three extra miles with the summer blend, plus a couple of more if you improve your driving, could take a midsize car with 23 mpg to 28.

Even if the price of gas jumps from $4.25 to $4.30 because the summer blend costs more, you could still save $2.40 a tank. Over the course of the summer, that could total $45.

“If you’re paying more, you might as well get something more, too,” Betancourt says.

Also, you could get a couple more miles per gallon by lightening your load. Get rid of bikes and luggage carriers and take the junk out of your car.