Choosing a higher octane gasoline will not improve the gas mileage of most cars, according to the Federal Trade Commission. Check your owner's manual for the recommended type of gasoline for your car to get the best results.
Octane ratings measure how well the gasoline prevents a rattling sound called engine knock. Gasoline is typically available in regular grade (around 87), mid-grade (around 89) and premium (92 or 93). These numbers may vary slightly in different states, but the specifications are clearly labeled on gasoline pumps.
If your car makes a pinging or rattling noise, switch to the next-highest octane grade. If this does not improve the engine knock, have a mechanic examine your car.
You can improve your gas mileage by driving within speed limits, avoiding rapid acceleration and combining errands into one trip. In addition, remove excess weight from your trunk or roof rack. Keep your tires inflated, your engine tuned and your air filters clean.
