HOUSTON --- Shell Oil Co. offers the following tips for cutting fuel costs:

1. Drive smoothly. Drivers should avoid heavy acceleration or braking. Speeding, rapid acceleration and braking can lower gasoline mileage by 5 percent at lower speeds around town and by 33 percent at highway speeds.

2. Replace dirty or clogged air filters. Replacing a dirty or clogged          air filter with a clean one can improve gasoline mileage by as much          as 10 percent. A car's air filter can protect the engine from impurities.

3. Keep the engine well-tuned and repair any problems immediately. If a car has failed an emissions test or is noticeably out of tune,          repairing the problem could improve gasoline mileage by 4 percent on average.

4. Make sure tires are not over- or under-inflated. Proper air pressure cuts down on fuel used while driving. Keeping tires at the correct pressure can improve gasoline mileage by more than 3 percent.

5. Minimize vehicle drag. Drivers need to keep the trunk and back seat clear of  unnecessary items that only add weight. Removing excess weight can improve gasoline mileage.

6. Use the recommended grade of oil in the engine. Following your manufacturer's motor oil recommendation can improve gasoline mileage by up to 2 percent. Look for motor oil that says "Energy Conserving" on the API performance symbol to ensure it contains friction-reducing additives. 

7. Choose a high-quality gasoline. Top automakers say that carbon deposits can build up on critical engine parts, which can decrease the power, performance and fuel efficiency of a vehicle. Audi, BMW, General Motors, Honda, Toyota and Volkswagen recommend using top tier detergent gasolines to help keep engines clean.

8. Use cruise control on major roads and in free-flowing traffic. Maintaining a constant speed can improve gasoline mileage.

9. Avoid idling. When drivers idle, they get zero miles per gallon.

10.  Avoid higher speeds. Gasoline mileage usually decreases when driving at speeds over 60 miles per hour.

11.  Plan outings to avoid separate trips. Drivers should combine errands into one outing to avoid short separate trips. This helps avoid unnecessary cold starts and keeps the car's engine running warm and more efficiently.