What Is the Difference Between Grades of Gasoline?

Comparing the difference between gasoline grades will allow you the chance to understand why some gas is more expensive and also how different grades of gasoline can benefit your car or damage your engine. All gasoline is derived from oil, however, how the oil is treated and processed will determine the exact grade and function. Placing the correct grade of gasoline in your vehicle can keep it running smoothly and will protect the engine from unnecessary wear-and-tear.


Gasoline in its earliest form was used to treat head lice and it was sold in small bottles. It wasn't until the 1920s when lead was added to gasoline to help improve the performance of automobile engines. Graded gasoline began to appear within this same time period, and there were two grades of gasoline available to purchase: regular grade and midgrade/plus. Grades of gasoline were organized by the octane level each obtained.


There are three main types of gasoline grades available in the United States; these include regular (87 Octane Rating), plus/midgrade (89 Octane Rating) and premium (92 Octane Rating). The grade of gasoline you need to use is determined by your vehicle’s manufacturer. There is no extra benefit to using premium grade gasoline if your vehicle calls for regular grade.


Regular, plus/midgrade and premium gasoline grades are all identified by their octane level. Octane levels describe the volatility within specific gasoline grades. Regular grade gasoline has a octane rating between 85 and 88, with the average being 87. midgrade, or plus, gasoline has an octane rating of 88 to 90, with the average being 89. Premium grade gasoline has an octane rating that is larger than 90, with the average being 92.


Different grades of gasoline burn differently. The lower the octane level, the easier the gasoline will burn. For powertrain control vehicles, the engines have been specifically designed to burn the optimum amount of gasoline, thus the exact grade has little effect on vehicle performance. All gasoline grades contain equal amounts of heat energy, however, their combustion level varies.


Gasoline grades inform you how easily the gasoline combusts within your engine. Lower octane levels can combust easier when compressed, which will make a knocking or pinging sound in your engine. Standard-performing vehicles are outfitted to use the correct amount of compression to eliminate internal combustion pings. Sports vehicles, or high-performance cars, benefit from midgrade to premium gasoline because their engines have been built for a higher level of compression for added driving power. There is no added benefit in midgrade to premium gasoline grades if your vehicle calls for regular grade gasoline.


About the Author

Jonathan McLelland has been a professional writer since 2005. He has worked as a story writer and editor for the international sitcom, “Completing Kaden,” as well as a proposal writer for various production companies. McLelland studied communication and theater at St. Louis Community College.