If you’re still planning to take a road trip this summer—perhaps to take your son or daughter to college—it might cost more than it would have last year.

While gas is still relatively inexpensive, prices have been edging up recently. According to AAA, prices for regular gas now average $2.33 a gallon nationally—about 20 cents more than one year ago.

The amount you'll pay depends of course on the gas station where you fill up. The gap between the highest and lowest priced gas stations within any given state currently averages 51 cents a gallon, says Patrick DeHaan, senior petroleum analyst at GasBuddy, a website and smartphone app that helps drivers find the best deals. That comes to a difference of about $10 if you're filling up the gas tank of a minivan.

There are also drivers who buy higher-cost premium gasoline for cars designed for regular fuel, according to a study by AAA. Based on current national average gasoline prices, mid-grade gasoline costs nearly 27 cents a gallon more than what you'd pay for regular. Premium gas costs 52 cents more. So if your car can operate on regular, but you opt for mid-grade or premium gas, you could be paying $5 to $10 more than necessary to fill that same minivan's tank.

Tips to Spend Less on Gas

There are things you can do to keep your gas expenses down. Among them:

Use a gas station app or website. GasBuddy, AAAFuel Finder and Gas Guru are among the resources that can help you find lower prices.

You're also likely to get a better deal at stations that are not located on major highways, says Michael Calkins, a manager at AAA. Of course, making a detour to pay less may not make sense. DeHaan says that based on current prices, a good rule of thumb is that for every mile you drive out of your way to purchase gas from a lower-cost station, you should save at least 2 cents per gallon. 

Calkins also says to make sure that when compare prices you consider only top-tier detergent gasoline, which is better for your car. 

Check the prices in the different states you'll visit. Prices can vary significantly because state gasoline taxes are different. DeHaan says he found that for a driver crossing the border from Ohio to Pennsylvania on Interstate 80, for example, it could cost 44 cents per gallon more to fill up in Pennsylvania. That's nearly $9 extra to fill up the minivan's gas tank.

Think about how best to pay. Some stations offer a lower price if you pay with cash instead of a credit card. The difference between the cash and credit price usually ranges from around 10 to 15 cents a gallon, says DeHaan, though he says it can be as much as a dollar.

Another option is to pay with a cash-back credit card. While the credit card price may be higher than the cash price, the reward you receive could make using the credit card a better deal.

It's worth noting that a rewards credit card could even provide greater savings than a gas credit card from a big oil company (such as Texaco or Chevron), says DeHaan. For instance, the Bank of America Cash Rewards Visa card offers 3 percent cash back on gasoline purchases, among other things, up to $2,500. That translates to a reward of about 7 cents a gallon at the current average national gas price. The Sunoco Rewards Credit Card, by contrast, offers only a flat 5-cents-per-gallon gas discount, though there is no limit on how much you can spend.

And if you plan to pay by debit card, don't assume that you are getting the cash price. Some stations could actually charge you the credit card rate instead. Check the posted prices at the pump. Selecting the debit option and entering a pin when you pump your gas is often a good indication your transaction will be handled as cash, says Lyle Beckwith, senior vice president of National Association of Convenience Stores, based in Alexandria, Va.