What is summer blend gasoline?

The primary difference between summer and winter blend gasoline is their Reid Vapor Pressure(RVP), which measures how easily the fuel evaporates at a given temperature. 

Summer-Blend Gasoline

• Lower RVP: Designed to be less volatile so it does not evaporate as easily in hot weather.
• Environmental Impact: Slower evaporation reduces the formation of ground-level ozone and smog.
• Energy Content: Contains approximately 1.7% to 2% more energy per gallon than winter blend.
• Performance: Results in slightly better gas mileage for drivers.
• Cost: More expensive to produce due to complex refining processes and the removal of cheap components like butane.
• Availability: Mandated by the EPA for sale to consumers from June 1 to September 15. 

Winter-Blend Gasoline

• Higher RVP: Designed to evaporate more easily to ensure engines start reliably in cold temperatures.
• Key Ingredient: Contains a higher percentage of butane (up to 10%), which is highly volatile and inexpensive.
• Performance: Provides slightly lower fuel efficiency because butane has less energy content than other gasoline components.
• Cost: Cheaper to produce because butane is more affordable than the additives used in summer blends.
• Availability: Typically enters the market around September 15 as regulations relax for the cooler months. 

Retail gas prices typically begin their seasonal climb in late February or early March.  Historically, prices reach their lowest point during the first week of February before rising through the spring. This upward trend often continues until prices peak around Memorial Day or in the early summer months. 

Key Drivers of the Spring Increase

• Refinery Maintenance: In February, refineries often shut down for “turnarounds” to perform maintenance and retool for summer production.
• Summer-Blend Transition: Refineries switch to producing summer-blend gasoline in March and April. This blend is more expensive to produce because it uses costlier additives to reduce evaporation in warm weather.
• Regulatory Deadlines: Terminals must purge winter-blend fuel by May 1, and retailers generally must switch to summer-grade gas by June 1.
• Rising Demand: Gasoline demand starts to increase in February and continues to grow as warmer weather and longer days encourage more driving, particularly during spring break and the start of the summer travel season.