How to Save on Gas July Fourth

July 3, 2007 — -- Getting out of town for the Fourth of July? Most Americans say they won't let high gas prices change their plans. So instead of changing plans, change your ways.

AAA says only 5 percent of the cars sold in the United States require premium gasoline, but premium accounts for 20 percent of all gasoline sold. What a waste. Say you use 20 gallons of gas per week. Regular costs an average of 20 cents less per gallon, so you'll save $4 per week or $208 per year.

Using a higher octane gas than the manufacturer recommends offers no benefit, but some people remain convinced that premium gas will make their cars go faster or get better mileage. It's just not true.

All the term "octane" refers to is a fuel's ability to help your car resist engine "knock." This knocking, rattling or pinging sound comes from premature ignition of fuel in your engine. Light knocking isn't harmful to your car, but heavy, persistent knocking can cause engine damage.

Your car is built to run on whatever grade of gasoline is recommended in your owner's manual. The vast majority of cars are designed to run on regular octane. If the manual says premium is "required," use it, but if it's just "recommended," ask your mechanic about using midgrade.

Most gas stations offer regular (usually 87 octane), midgrade (usually 89 octane) and premium (usually 92 or 93). These levels vary from state to state. For example, one state may require all premium gasoline to have an octane of 92 or above while another state may allow 90 octane to be labeled premium. When you read your owner's manual, be sure to note the precise octane level your car requires. Then look for that level rather than relying on a generic term like "regular" or "premium."

There are other ways to save money on gas. Here's a novel idea: try driving the speed limit.

Driving 55 mph instead of 65 improves your fuel consumption by 20 percent, AAA says. Erratic acceleration and braking burn fuel too up to 50 cents a gallon.