Fueled Up for Summer?

Welcome to May. Warm weather is finally coming — time for planting, fishing, opening doors, stowing winter gear, patio  sitting and dining, setting up grills and switching from winter to summer gas in your car.

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OK so that last item may sound confusing as it was to me this week, but it's true. As the season goes from winter to summer, car fuel changes. Usually, this semi-annual switch of winter to summer gas goes unnoticed by most motorists, except at their next fill-up.

I never understood about this seasonal gas changeover, until reading a news article this week, and learned (a lot) about it.

Filling a car's gas tank costs more in summer months (here in the U.S. I'm not sure in other countries). Today, the average U.S. gas price nationwide is up about 15 cents from the past month. That's not demand leading to higher pump prices — it's all about the gas.

Why not continue using cheaper winter gas? It's because the so-called winter gas contains a cheaper ingredient, butane, that helps cold weather starting. Summer gas contains a more costly ingredient, alkylate, which is better for hot weather driving. 

Most of us are familiar with the use of butane as lighter fluid and an ingredient in fuel for gas grills and camping. As a fuel, it's less costly than other gas components; however, its high volatility limits how much can be included in summer car fuel.

Another factor leading to the higher gas cost is that refineries are switching from the winter to summer gas supplies and doing maintenance, which, in turn, reduces the fuel supply.

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U.S. environmental regulations require that gas sold in summer months be less susceptible to evaporation. That requires refiners to replace evaporative gas components with ones that have the opposite characteristics which can be more expensive, according to the U.S. Energy Information Administration.

This switchover happens in March and April. The Environmental Protection Agency (EPA) requires refineries to have a summer blend in their system by May 1. Gas stations must comply by June 1. Refineries produce than 14 types based on different state regulations. Because of this production takes longer, the overall yield per barrel is lower, and motorists can pay up to 15 cents more per gallon in summer months.

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Why does summer gas differ from winter gas? Here's what I learned. Winter fuel has a higher Reid Vapor Pressure (RVP), a measure of how easily fuel evaporates at increased temperatures. This means that it evaporates easier in colder temps, letting cars start faster. If the fuel didn’t evaporate fast in cold temperatures, a car engine would start hard and run rough (which no motorist would like). To achieve this, refineries blend winter gasoline with butane, an inexpensive additive with a high RVP. 

Most of us are familiar with the use of butane as lighter fluid and an ingredient in fuel for gas grills and camping. As a fuel, it's less costly than other gas components; however, its high volatility limits how much can be included in summer car fuel.

Once summer temperatures heat up, high RVP gasoline can evaporate faster which can lead to increased emissions, ground level ozone and air pollution (smog). That's why U.S. federal law restricts sales of gasoline with an RVP greater than 9.0 psi from June 1 through September 15.

To comply, refiners reduce the amount of butane in the gas with pricier additives, leading to
higher gas prices in summer. This blending process also takes longer adding to the cost.

Some states set lower summer RVP standards to further limit emissions. California has a 7.0 psi limit. Due to the state’s climate, refiners can sell summer gas as early as April 1 and as late as October 31. Other U.S. cities such as Phoenix, AZ, extend summer fuels into the fall. Also, during emergencies that cause fuel shortages, the EPA has relaxed its rules. 

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So what's the good news? Better MPG. Cold weather and winter driving conditions reduce fuel economy which, in turn, can reduce mileage as gas blends in winter contain less energy than those in summer. According to the EPA, the summer blend has 1.7% more energy, so, your MPG could be better in summer months to offset some of the added cost when filling up.

Also, gas costs are expected to level off as the winter to summer gas change is done and not expected to rise much in coming weeks. The average price of gas in the U.S. today is about is $3.66 per gallon. Currently, the average price per gallon in NH is about $3.57.

These figures are well below the highest U.S. gas prices. In California, a gallon of regular gas is priced at an average of $5.40 per gallon, followed by Hawaii, Nevada, Washington and Oregon at between $4.50 and $4.81 per gallon. The country's lowest gas prices are in Mississippi, Colorado, Oklahoma Louisiana, Arkansas averaging from $3.10 to $3.20.

In case you consider these costs high,, they're not when compared to international gas costs: residents of Hong Kong pay the highest gas prices with 1 gallon averaging $11.43 followed by Iceland at $8.91 and Monaco at $8.49 per gallon just a few examples.

Summer Driving Tips. According to the Automobile Association of America (AAA), there's ways to lessen the higher cost of summer gas by following a few driving habits to conserve fuel: Keep tires properly inflated; avoid rapid acceleration and braking; use cruise control for highway driving when it’s safe to do so.

Now I know something new to me, and so do you.

Your Turn — Have you also noticed an increase in gas prices in your state?