Summer road trips used to be associated with freedom; with gas prices still hovering at record marks, they're more likely to be associated with costs.

Here are 10 simple ideas to make your car more fuel-efficient.

1. Check your owner's manual to find out what fuel octane rating your car's engine needs then buy it. Resist the urge to buy higher-octane gas for "premium" performance, unless your car requires it.

Octane has nothing to do with the gasoline's performance, merely its volatility factor in the combustion chamber. Translation: If your manual doesn't specify that your car needs premium gas, there's no reason to pay more for it.

2. Keep your tires inflated to the proper levels. Under-inflated tires make it harder for your car to move down the road, which means your engine uses more fuel to maintain speed.

In fact, a single tire, under inflated by two pounds per-square-inch PSI), increases fuel consumption by one percent. Check your owner's manual or the decal in your car's doorjamb for correct inflation levels.

3. Make sure that you change the oil and maintain your car's powertrain according to your owner's manual. This will ensure that your car's engine will operate at maximum efficiency, thus providing the best fuel economy.

Dirty air filters, old spark plugs and low fluid levels can affect engine performance and fuel efficiency.

4. Lay off the accelerator. A car uses more fuel under hard acceleration. So don't race up to red lights or stop signs, avoid quick "jackrabbit" starts, and don't goose the throttle to jump into holes in traffic.

5. Avoid high speeds on the highway. As your speed increases, the aerodynamic drag increases in exponential fashion, so the engine has to work harder - and use more fuel- to maintain your speed and move the car through the atmosphere.

Driving 62 mph instead of 75 mph can reduce fuel consumption by as much as 15%. If you have it, cruise control is a great way to maintain a safe, fuel-efficient highway speed while cutting down on fuel-burning deceleration/acceleration.

6. Lighten the load. Heavier vehicles use more fuel, so clean out unnecessary weight in the passenger compartment or trunk before you hit the road.

7. Use the A/C sparingly. The air conditioner puts extra load on the engine, forcing more fuel to be used. On average, a car operating with the air conditioning engaged uses about 20% more fuel.

If it's just too hot to bear without A/C, try to keep it set at around 75 degrees.

8. Keep your windows closed. Wide-open windows, especially at highway speeds, increase aerodynamic drag and the result is up to a 10% decrease in fuel economy. If you want to have fresh air coming into the vehicle, run your climate system on "outside air".

9. If you own a pickup truck, consider getting a tonneau cover or a tube-style tailgate. These items will help to minimize drag over the cargo bed and allow the vehicle to slip through the air stream more efficiently.

10. Avoid long idling. If you anticipate being stopped for more than one minute, shut off the car. Contrary to popular belief, restarting the car uses less fuel than letting it idle.