When a product costs more than the standard and is labeled with terms like “premium” and “plus,” the assumption is that the product will perform better than the standard. For some cars, this is true. High-performance vehicles are designed to work with premium gasoline, but these are often sports cars with specific requirements.
What is the Difference?
Octane—one of the hydrocarbons that make up gasoline—is the component measured on the gas pump. Not the amount of octane itself in the gasoline, but how the gasoline mixture compared in combustion tests against a specialized test fuel. This number determines how long the fuel can be compressed with air before igniting. Sometimes the fuel/air mixture will ignite from compression without a spark. This causes the engine to ‘knock.’
Gasoline mixtures are compared to the test fuel and rated based on their performance—do they knock very often? If not, the mixture is rated premium. High-performance engines, such as sports cars or some older cars, have higher compression ratios and would knock without premium gasoline.
What About Most Cars?
Most modern cars have a specific compression ratio that tolerates lower octane fuels without knocking. Regular gasoline will work just as well as premium without the additional cost per gallon. There’s no significant improvement in vehicle performance with premium gasoline, and many high-performance vehicles can function without knocking on regular fuel.
If you’re especially concerned about high-performance in your sports car, then premium gasoline would be the best choice. But you wouldn’t be doing the vehicle any damage by filling up with regular if you needed to do so. For the majority of vehicles on the road, however, there is no noticeable difference with premium gas and no benefit to your engine.