At $3.309 a gallon, the Rapid City area's average gasoline price Saturday was only 6 cents below the all-time high set March 14.

The price here is less than a penny below the national average, which appears poised to rise further in coming weeks as gasoline supplies tighten.

Oil's surge above $100 in the past month has boosted gas prices so far this year, but analysts now expect gas prices to continue rising regardless of what direction crude takes. The Energy Department expects prices to peak near $3.50 a gallon later in the spring, but many analysts predict the spike could approach $4.

That is because gasoline supplies are falling, in part because producers are cutting back on output of the fuel due to the high cost of crude. They are also in the process of switching over from producing winter grades of gasoline to the less polluting but more expensive grade of fuel they are required to sell in the summer.

There are some things motorists can do, however, to stretch their fuel dollars.

AAA South Dakota offered these tips for improving your fuel economy:

* Buy cheap gas. Use premium only if your owner's manual says you should. You may think you're doing your car a favor by buying premium, but you aren't. For most cars, the recommended gasoline is regular 87 octane. Also, don't "top off" when filling your tank. Most of that fuel either remains in the hose or evaporates.

* Check your tires. Underinflated tires rank as the most common reason for poor fuel economy. Surveys show that one out of every four cars on the road today has at least one extremely low tire. One in every three pickups, vans and SUVs has the same problem. Gas mileage drops as much as 2 percent for every single pound of pressure your tires fall below the recommended level. Investing five minutes every two weeks with an air hose and a tire gauge will save you. Check your owner's manual or the sticker in your glove compartment or on a door jamb for recommended tire pressures. Do not go by what is on the tire; that is the maximum.

* Check your air filter. If it's dirty, buy a new one and put it in; it's very easy to do. You can do it yourself; look in your owner's manual for information. Replacing a dirty air filter can increase your gas mileage by as much as 10 percent.

* Get a tune-up. Old, dirty spark plugs can reduce fuel economy by 30 percent. Other bad components under the hood can cause your engine to waste even more fuel.

* Plan ahead. If you have to drive far to do your shopping, make sure you buy everything you might need for several days. Consolidate errands. Cold engines use more fuel than warm engines. Also, visit shops closer to home.

* Slow down. Stay within posted speed limits; avoid rush-hour driving; don't drive aggressively; and avoid unnecessary idling. Quick, jackrabbit starts and sudden stops waste fuel and are hard on your vehicle. On the highway, keep an eye on your speed. Gas mileage decreases rapidly at speeds above 60 miles per hour.

* Roll down the windows. Turning on your air conditioner causes your vehicle to use 10 percent more fuel. Check the outside temperature, and if it isn't too hot, consider rolling down windows instead. Younger kids love open windows. So do dogs. However, on the highway, roll those windows back up. The extra drag produced by open windows actually tends to decrease your fuel efficiency.

* Get a rebate. Pay at the pump using a gas rebate credit card. Gas stations formerly charged more if you used a credit card, but no more.

* Lighten your load. Take unnecessary weight out of trunks, pickup beds and back seats. Every extra 100 pounds can cost you a mile a gallon.

* Tighten that cap. By some estimates, loose, missing or damaged gas caps allow 147 millions of gasoline to vaporize annually.

* Don't buy a device. Be skeptical of claims for devices that will improve your mileage. Some will even harm your car's performance.

* Consider a hybrid. Hybrids and alternative fuel vehicles are getting better, with more power and greater fuel economy.