The only thing about gas prices that remains constant is change. There are a lot of reasons for the never-ending roller coaster at the pump, whether it’s because of supply and demand, refinery issues or global conflict.

One reason that may be less thought about is the weather. 

Depending on where you live and the time of the year, your car could have summer or winter-blend gasoline in its tank. There are government regulations on the type of gas we use, and a lot of that is because of the temperature outside.

Reid Vapor Pressure (RVP) is a common measure of and generic term for gasoline volatility, and one of the key differences in the two blends. The EPA regulates the RVP of gas sold during the summer to help reduce evaporative emissions from gas that contributes to ground-level ozone and air pollution.

The higher the RVP, the easier it evaporates.

The type of gas your car is using will affect your wallet, car and the environment. So, what are the differences? 

Every September, gas refineries are required to transition production from summer-blend to winter-blend gasoline. This is around the same time of the year that both gasoline demand and temperatures drop.

Winter-blend gasoline has a higher RVP, so it evaporates easier. To give it a higher RVP, refineries make it with more butane, which also helps the gas in your car ignite easier during the cold weather.

Butane is a relatively inexpensive additive to gasoline, so that’s why gas prices can drop anywhere from 10 to 30 cents per gallon around the fall when gas stations make the switch. 

If winter-blend gasoline is cheaper to make and cheaper at the pump, why can’t we just use that all year? The EPA regulates gasoline emissions during the summer that are a major contributor to ground-level ozone, or smog.

That’s why summer-blend gas has less butane, which gives it a lower RVP and makes it harder for it to evaporate. While it’s better for the environment, since it has lower emissions, it’s also more expensive to produce.

When summer-blend gasoline hits the pumps in late spring, gas prices can increase up to 15 cents per gallon, along with the increased demand because of more travel during the summer, it can be even more.

On the plus side? Since summer-blend gasoline has less butane, it’s more efficient. According to AAA, summer-blend contains about 1.7% more energy than winter-blend gasoline, which equates to more miles per gallon on the road. 

Most people still have to rely on personal vehicles for transportation regardless of gas prices. Whether prices are high or low, there are some things we can control to save some money at the pump.

• Drive a hybrid or fuel-efficient vehicle
• Keep tires properly inflated
• Avoid rapid acceleration and braking
• Use cruise control on the highway when possible
• Remove unnecessary, heavy items from the back seat or trunk to reduce your vehicle’s weight
• Carpool and take turns driving is possible

Our team of meteorologists dive deep into the science of weather and break down timely weather data and information. To view more weather and climate stories, check out our weather blogs section.