Gasoline pumps are commonly labeled regular, mid-grade, or premium. The difference in the fuel is the octane number. Regular is usually 87, mid-grade 89, and premium 92-93. The higher the octane number the more the fuel resists combusting under compression. If the octane rating is too low for your engine, the engine may “ping” due to the fuel igniting prematurely. It is wise to use the recommended octane number that is listed in your owner’s manual. Use higher octane fuel only if your engine “pings” or “knocks”. If your engine runs fine on the recommended octane number, stay with that grade of fuel and not waste money on a premium fuel.
Use Lower-octane gasoline: Buy the lowest grade or octane of gasoline that is appropriate for your car. Unless your car requires premium gasoline, filling up your car with high-octane fuel is a waste of money. That pricey premium fuel won't boost your car's fuel economy or performance in the least, so skip it.
If you're not sure what grade of fuel works best for your car, open up your owner's manual and take a look. As long as your engine doesn't knock or ping when you fuel up with regular unleaded, you're good to drive on this much cheaper gas. Passing on pricey premium gasoline could save you hundreds of dollars a year.
Don't top off: when filling your car's gas tank. Any additional gas is just going to slop around or seep out. Stop pumping at the first indication that your tank is full when the automatic nozzle clicks off. Also, gas will evaporate from your car's gas tank if it has an escape. Be sure to tighten up that gas cap each time you fuel up your car. -Accelerate more gradually. Start off slowly, "the pedal to the metal" just cause's the use of more fuel. -Anticipate your stops. Watch ahead of you by a half a block or so, you can see a light changing red and take your foot off the gas earlier. By coasting instead of driving under power, you're burning less fuel. -Drive a little more slowly. Going 5 or 10 miles per hour lower than the highway speed saves lots of gas, and probably won't add much time to your trip. (ever notice the car that flew past you, and a few miles later, that car was waiting at the next light) -Warming up your vehicle in the driveway wastes gas, but, do drive slowly for the first few minutes instead to bring your engine to optimal driving temperature. -Smooth, gradual acceleration increases fuel mileage; rapid starts waste gas. Try to maintain a steady rate of speed and take advantage of timed traffic lights. -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. -Proper tire inflation and wheel alignment decrease road resistance and increase mileage. Check tire pressure monthly and rotate tires using your vehicles specific maintenance schedule. -Drive less by planning ahead. Try to do all your errands in one trip and plan the most efficient route. -Keeping your engine properly tuned can save you big bucks. DOE says fixing a car that's noticeably out of tune can improve gas mileage by 4 percent. -You should check and replace air filters regularly. Replacing a clogged air filter can improve your car's gas mileage by as much as 10 percent. Do not fill up at a gas station when they are getting fuel. Water is present in underground tanks and generally does not cause a problem since the fuel pick up for the gas pumps is several inches from the bottom. But when a semi-tanker is “dropping fuel” the water at the bottom of the underground tanks mixes with the gas. If you are pumping gas in your vehicle at that time, you may get excessive moisture in your tank.