What is the Difference between Summer and Winter Fuel?

Gas prices fluctuate day to day, but have you ever noticed that they also seem to change with the seasons? As summer approaches, you can usually expect a slight price hike on gas, while winter is usually marked by lower prices at the pump. Here's why.

The seasonal gasoline transition

The seasonal gasoline transition occurs twice every year in the United States. Although it sounds like an ancient oil festival, it is not accompanied by wild celebrations and revelry in oil producing states, such as Texas and Oklahoma. Instead, it is simply when oil companies switch their gas supplies from summer grade fuel to winter grade fuel or vice versa. The seasonal gasoline transition is one of the reasons gas prices rise in the summer and go down in the winter.

The Reformulated Gasoline Program

The Reformulated Gasoline Program (RFG) owes its existence to the 1990 Clean Air Act Amendments. The switch from winter to summer gasoline blends began in 1995 as an attempt to reduce pollution. Summer gasoline uses different fuel additives to prevent it from evaporating too quickly. How quickly a gas evaporates is based on its Reid Vapor Pressure (RVP). The higher a gasoline's RVP, the quicker it evaporates. All gasoline has to be below 14.7 psi or it would no longer be liquid. Summer gasoline is usually between 9.0 and 7.8 psi. That's something to think about the next time you're filling up the tank.

Higher gas prices in the summer

The ultimate question when it comes to the differences between summer blend and winter blend gasoline is why it goes up so much in the summer. The truth is that there are many factors. Lower RVP gasoline costs more because of the additives that are needed to keep the RVP low. Demand is also higher in the summer. In addition, during the spring months, most energy companies in the United States conduct maintenance on their refineries, which limits their capacity. These maintenance shut downs are part of the seasonal gasoline transition and lead to a limited supply of fuel. This lessening of supply while demand is greater has a large effect on gas prices.

The environmental impact

The justification for lower RVP gasoline blends stems from the desire to lower emissions and smog during the summer months. With less gasoline evaporating into the atmosphere, air quality increases.