Whether you're off to the Chicago Air and Water Show presented by Shell or just out for some fun in the sun, families across the country will be heading out on the highway this summer for the great American road trip adventure. In fact, according to the Travel Industry Association of America, about 86 percent of all domestic summer vacations are taken by car, truck or RV.

To help motorists enjoy their vacations without breaking the bank, Shell offers five easy ways to maximize a road trip budget.

Start Out Slow. While you may be anxious to reach your destination as quickly as possible, be sure to observe the posted speed limits. Avoiding high speeds not only will help conserve gasoline, it also could help you avoid a costly speeding ticket.

Find the Free Fun. For some inexpensive entertainment along the way, look for free roadside attractions, such as the world's largest ball of twine in Cawker City, Kan., or the Eiffel Tower Replica in Paris, Tenn. Another good option is a nearby event with multiple activities, such as the Chicago Air and Water Show -- with exhibitions from jets and stunt planes to a movie premiere of Tugger and a concert by Jim Belushi and the Sacred Hearts -- because there is something for everyone to enjoy. State parks, museums and historical sites also can prove to be bargain destinations. For theme park lovers, be sure to check online for special discounts on pre-purchased tickets and other value- added deals.

Save at the Pump. When it's time to fill up, stretch the road trip budget by using a credit card that offers rebates on gasoline. For example, consumers who use the Shell MasterCard from Citi Cards earn a 5 percent gasoline rebate on Shell gasoline purchases -- that translates to 10 cents per gallon on gasoline priced at $2 per gallon. Consumers also earn an additional 1 percent in Shell gasoline rebates on all other purchases they make with the card. So, by using the credit card for everyday purchases throughout the year, families can save enough to pay for the gasoline used during their entire summer road trip.

Book a Hotel that Offers Extras. When selecting a hotel or motel, choose one that offers extra value, such as a free night's stay, complimentary breakfast or discounts on area restaurants and attractions. Some hotel chains now even offer free to-go breakfast bags and snack packs for those who can't wait to hit the road again.

Prepare for the Unexpected. The last thing you want to deal with is a flat tire or a dead battery, but unfortunately these things can happen. To minimize the stress and cost involved with using local towing services and repair shops, look into roadside assistance plans before you leave. But be sure to shop around for the best deal. Your car's manufacturer may offer free roadside assistance. Even some cellular telephone services now offer 24-hour roadside assistance for as little as $2.99 per month.