Fueling the Season: Ensuring Cleaner Winters with Butane Analysis

As we approach the winter season it becomes essential to have winter grade gasoline to ensure our vehicles run smoothly in weather conditions. The petroleum industry commonly uses butane blending to create winter grade gasoline with optimal vapor pressures.

Understanding Butane Blending

Butane is a hydrocarbon compound found in gas and crude oil that is used as a component when producing winter grade gasoline. Blending butane into gasoline involves mixing these two elements to achieve specified regulatory vapor pressure. Butane having a Reid vapor pressure (RVP) of 52 psi is inexpensive and plentiful, making it an ideal additive for gasoline.

Why blend Butane into Gasoline?

When it comes to creating winter grade gasoline, vapor pressure becomes a factor. The vapor pressure measures a fuels ability to turn into vapor at ambient conditions. In different climates the vapor pressure of gasoline becomes crucial, as it influences the fuels performance. Gasoline‘s RVP must be below 14.7 psi, or atmospheric pressure, in order to check it’s volatility.

Depending on the state and month, gasoline RVP’s are regulated and may not exceed 9 psi or 7.8psi for summer-grades. Following the summer driving season winter blends begin coming out in September, with the first increase in vapor pressure allowed September 15th. Summer grade fuels might include butane in lower quantities around 2%, while winter grades can contain about 10% butane in its blend.

During freezing temperatures engines require fuels with higher vapor pressures for efficient cold starts. Low vapor pressure can lead to difficulties in fuel evaporation resulting in issues, like starting and stalling. Butane, due to its boiling point, greatly increases the vapor pressure of gasoline making it an excellent choice for weather conditions. Vapor pressure also plays a role in determining emissions. As we know, emissions are the volatile organic compounds, also known as “VOC’s”, that are released into the atmosphere from fuel during storage, refueling, and vehicle operation. By using butane to manage vapor pressure in our gasoline, we can reduce emissions and minimize impact to the environment.

When blending butane into winter grade gasoline it’s important to strike a balance between vapor pressure and considerations for engine performance and the environment. This can vary depending on weather conditions and regulatory requirements. The severity of winter weather in a region is crucial in determining the vapor pressure. Colder climates need gasoline with higher vapor pressures to ensure reliable cold starts.

Is your Gasoline up to spec?

The US government has established standards for gasoline vapor pressures that the industry must comply with in order to control emissions. The Environmental Protection Agency or “EPA” carry out these regulations and ensure refineries and producers are adhering to them.  It is important to understand the regulations as they may differ from one region to another due to differences in temperature. To accommodate temperature fluctuations throughout the year fuel producers may adjust the ratio of butane blending seasonally. Higher levels of butane content are suitable for winter fuels while lower concentrations may be used during months.

Terminals and truck racks often buy and store butane to blend with gasoline to specific vapor pressures. In this process butane is delivered by truck for storage in the blending operation. It is key that the butane being delivered meets client specification.

How can SPL help?

To ensure compliance with these regulations and have on-spec product, fuel producers and refineries should test their product through laboratories with ASTM accredited equipment and product expertise. SPL’s Finished Product laboratories can analyze butane for composition including benzene, oxygenates, sulfur, residues and corrosive compounds. We also offer full ASTM D4814 Gasoline spec. to ensure your fuel and blends meet specifications 40 CFR Part 1090. To find out more about how SPL can ensure your winter butane blends are up to spec, contact us at info@spl-inc.com.

Zak Mortensen

Senior Sales Representative

Zak has dedicated the past ten years to the field of commodity inspection and laboratory testing. He has also accumulated over a decade of experience in laboratory instrument sales. Zak is enthusiastic about leveraging his expertise to assist customers in achieving their specific objectives. His approach values cultivating enduring connections over mere transactions. He firmly believe that honesty and providing value are the cornerstones of establishing trust. Beyond Zak’s professional life, he derivs enjoyment from crafting high-performance engines for automobiles and HD motorcycles. 


Tom Benz

Technical Director

Tom Benz has been with SPL since 1995, bringing six years of experience from the oil and gas industry. Starting in the Wet Lab, he specialized in wet chemistry titrations. After two years, he transitioned to the ASTM Lab, where he mastered physical properties testing on crude oil. In 2002, Tom became the ASTM Laboratory Supervisor, overseeing the team for five years before becoming Assistant Manager for the Houston Laboratory. In 2006, he joined ASTM International, managing the ASTM Proficiency Testing Program for Crude Oil and #2 Diesel Fuel at the SPL Houston ASTM Laboratory. Today, Tom serves as the SPL Houston Laboratory Technical Director and ASTM International D02 Representative. Outside of work, he enjoys caring for his rescue Miniature Schnauzer, Abigail, and embarking on adventures with his wife. in his beloved 1997 Chevrolet Tahoe.