What Are Michigan’s Summer Gas Laws, and How Does It Affect You?

Starting in June, the state of Michigan will begin implementing its annual fuel and gas laws that have helped reduce emissions and smog in major communities across the state for years.

The laws went into effect on June 1st, and at least eight counties are specifically being targeted to help lower the amount of pollution.

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Residents in Lenawee, Livingston, Macomb, Monroe, Oakland, St. Clair, Washtenaw, and Wayne Counties will all be affected by this rule change, where gas can only be dispensed that does not exceed 7.0 pounds per square inch in vapor pressure.

What is the Summer Gasoline Program?

The initiative was introduced in 1996 by the National Ambient Air Quality for ozone in the Detroit Area. They had monitored violations that were outlined in the EPA's Clean Air Act, and needed to enforce a rule to bring these areas into compliance. The program is essential as it makes sure the state still receives federal highway funding dollars.

Tim Boring, who is the director of the Michigan Department of Agriculture and Rural Development said their actions echo what Governor Gretchen Whitmer has proposed to protect Michigan's environment.

"Our department is committed to protecting Michigan's environment as our industry continues to implement climate-smart practices focused on combating climate change in Michigan."

What Does Reducing Gasoline's Vapor Pressure Do?

Gasoline volatility is measured by something called the Reid Vapor Pressure. Basically, it tells us how explosive the gasoline, and other petroleum products, are, and it's measured when the gas is at roughly 100 degrees fahrenheit.

RVP is measured in pounds per square inch, and the higher the RVP, the more volatile the fuel is, which means it evaporates more easily and can contribute to air pollution. When the RVP is lowered, it means the fuel is less volatile, and won't contribute to air pollution as much.

In most areas of the country, the RVP of stored fuel is not allowed above 15 RVP, though most will keep it a bit lower than that. During the summer, however, many major cities will enact EPA laws, and fuel laws, that require reducing the RVP. Most cities that have such laws cap it at around 9.0 RVP, while some cities in Colorado, Nevada, Oregon, Texas, and Utah, will cap it at 7.8 RVP.

Michigan is one of the most strict when it comes to summer fuel RVP in the Detroit area, capping it at 7.0 RVP.

Will a Lower RVP affect my Gas Mileage?

Yes, but probably not in the way you think.

Many gas stations store gasoline at a higher RVP so they can hold more fuel, but it actually creates a negative effect on your car's gas mileage. The more volatile the gasoline, the lower your gas mileage could be.

The octane rating will be higher, and you might get a little more "pickup" when you press down on the gas pedal, but if you're just a typical city, or daily driver, and don't need that extra boost in your daily drive, a lower RVP can actually increase your gas mileage.

So if you notice a few extra miles on a tank during the summer, that might be why.