Octane Fuel Ratings and Your Engine
These days, information about boats and motor manufacturers say their engines can run on 87 octane fuel, but when you pump 87 octane, is that what you are really getting? It might not be as straightforward as you think.
The small yellow squares on fuel pumps indicate the octane rating for each fuel grade. The numbers may be anywhere from 87 to 93. When you pull up to the gas station, you may select your fuel grade and therefore, your octane rating as well.
Many boat owners and car drivers associate a higher rating with higher quality. But it may be an incorrect boat fact to assume that higher octane ratings equal higher performance. Gas companies buy into this as well labeling lower ratings as “regular” fuel and higher ratings as “super.” While some may believe that paying more means better quality, the truth is, they might just be paying more for the same product.
On newer model engines equipped with computers to control all engine functions, using high octane in place of a specified lower octane, the computer is likely to think the cleaner burn (by way of a sensor in the exhaust path) is the result of a lean running engine therefore compensates by adding more fuel to the mix and decreasing miles per gallon.
Information about boats and vehicles have said over and over that high octane fuels burn cleaner or more completely, giving more power and better fuel economy. The fact is the octane rating for gasoline has nothing to do with the amount of power in your boat or car. The octane rating simply indicates how much a fuel can be compressed before igniting. The higher the number, the less likely it is to ignite under pressure. So what does this mean for boat owners? Lower octane fuel may cause the gasoline to ignite too early, which scientifically may reduce engine output. But most engines are made so efficiently already, that the regular octane rating is sufficient and there is no need or benefit to running premium fuel.
If you run a turbocharged or supercharged boat or car, or you have additional features or information about boats specifically designed for these higher octane fuels, they may be beneficial. But for most boat owners, regular fuel can be just as efficient. To determine the boat facts surrounding your specific model and to evaluate which octane rating is recommended for your boat, check the owner’s manual. Some models may have an indicator on the gas cap itself.
With an engine designed for regular gas, you won’t see any difference in using a premium blend. However, if your engine is specifically designed for high octane fuel, it is best to stick with the manufacturer’s recommendations.
If you run a standard boat motor and you’re not a high performance or boat racer, you’ll be perfectly pleased with the performance of a regular octane fuel. It is generally not worth the increase in price for the minimal increase in gas mileage you may or may not find with a higher octane fuel.