Putting supreme (premium) gasoline in a regular car that only requires regular fuel is generally safe, but it is a waste of money. Your car's engine is designed to run optimally on a specific octane rating, and using a higher one provides no meaningful benefit in performance, fuel economy, or engine cleanliness. The key factor is the octane rating, which measures a fuel's resistance to uncontrolled ignition, or "knocking." Using premium fuel in a car engineered for regular is like using high-performance racing oil in a commuter car—unnecessary and costly.
Octane Rating Explained
The octane number (e.g., 87 for regular, 91-93 for premium) indicates the fuel's stability under pressure. High-performance engines with high compression ratios or turbochargers generate more heat and pressure, making them prone to pre-ignition or knocking, which can damage the engine. These engines require high-octane fuel to prevent this. Conversely, an engine designed for 87-octane fuel has a compression ratio that will not cause knocking with regular fuel. Its engine control unit (ECU) is calibrated for 87 octane, so it cannot advance the ignition timing to take advantage of premium fuel's higher resistance to knock. Therefore, you pay more for zero gain.
| Supporting Data Point | Explanation |
|---|
| 87 Octane | Standard "regular" fuel for most non-performance vehicles. |
| 91-93 Octane | Typical "premium" fuel range in the United States. |
| 10:1 to 11:1 | Example compression ratios for engines that often require premium fuel. |
| 8:1 to 10:1 | Common compression ratios for engines designed for regular fuel. |
| $0.20-$0.60/gallon | The typical price premium for premium over regular fuel. |
| Federal Trade Commission (FTC) | States that using higher-octane fuel than recommended offers no benefit. |
| 0% HP Gain | Most independent tests show no measurable horsepower increase. |
| 0% MPG Gain | No significant improvement in fuel economy for regular-car engines. |
| Top Tier Gas | A detergent standard; available in both regular and premium grades. |
| Knock Sensor | A device that allows engines to use lower-octane fuel safely by adjusting timing. |
The only time you might notice a difference is if your car is specifically designed for regular fuel but is experiencing knocking due to carbon buildup or a faulty sensor. In that case, premium fuel might mask the symptom temporarily, but the underlying mechanical issue needs to be diagnosed and repaired by a professional. For everyday driving, always follow the octane recommendation in your owner's manual or on the fuel door. If it says "Regular Unleaded," that's all you need. Save your money for something else.
