Why Is Butane A Common Additive In Gasoline Blends?

Q Two further reasons that influence lower fuel economy in the winter were not mentioned (in a recent piece).

Winter gasoline is less thick because it includes more butane, resulting in fewer pounds of gasoline per gallon. Because the energy content of hydrocarbons (BTUs per pound) is essentially constant, less energy per gallon and lower mileage are the result.

Is mileage affected by cold lubricants in the transmission, wheel bearings, and differentials? Is there a difference in rolling resistance when the tires are colder? In the snow, there has to be more resistance and drag, right?

A The increased percentage of butane in winter blends, which is generally around 2% in summer blends, is to improve the volatility and vapor pressure of the gasoline, allowing it to evaporate more easily in cold conditions. When you consume gasoline in your engine, keep in mind that it must be in vapor form.

Butane is also less expensive than gasoline, which could explain why gas costs at the pump are lower in the winter.

In addition to having a higher percentage of butane, “winter blends” have other additives like anti-icing chemicals, which don’t give as many BTUs of energy to burn and convert into electricity. As a result, the overall energy per gallon of fuel in your tank is lower.

Yes, it takes more power and hence more fuel to move your car down the road until lubricants warm up, thin down, and flow more smoothly, and until tires warm up a bit to enable greater flex and less resistance to rolling.

Q I recently purchased a 2006 Chevrolet TrailBlazer EXT LS. Along with the usual 2WD, 4WD High, and 4WD Lo, this car has a “4WD Auto” option.

When the roads are wet, snowy, or slippery, my wife wants to know if she can leave it in 4WD Auto all the time. I’m curious if this will cause any damage to the vehicle.

A “4WD Auto” is exactly what it sounds like: a four-wheel drive system that is totally automated. It is entirely safe to drive the vehicle in this arrangement all year long, not just when it is slick.

The drivetrain will not be harmed in any manner. More crucially, if the drive wheels slip, it will automatically engage four-wheel drive practically immediately. In all conditions, this provides the driver with substantially superior traction and a lot safer, more secure car.

Q We have an 87,000-mile 1997 Dodge Grand Caravan with a 3.8-liter engine and front-wheel drive. The speedometer will unexpectedly jump to 120 mph and then back to zero numerous times before returning to normal. This appears to happen every time the automobile accelerates from a stop, at which point the car jerks and hesitates before regaining speed.

It also happens at random while we’re traveling down the highway (thankfully no jerking). It doesn’t always go from zero to 120 mph; sometimes it’s more moderate, going between 20 and 60 mph.

The Dodge dealership has looked at it three times with no luck. I asked them to replace the speed sensors, but that didn’t help. They speculated that it might be a wire-harness issue (our battery was allegedly loose and dug into the harness), but they didn’t examine it further. They claim it can’t be the dash computer because the jerking we’ve experienced isn’t caused by it.

We’d like to get this fixed, but we’re tired of having to leave the car off at the dealer and sharing a car. Do you have any materials that could be useful to us?

A There are various possible causes for inconsistent speedometer operation, according to the diagnostic information in my Alldata automobile database, which you may get at local public libraries. Check the speed signal provided to the PCM by the “distance speed sensor” used in the three-speed automatic transmission, or the transmission control module used in the four-speed transmission, if there are no error codes or problems with the PCM. After that, look at the wiring between the TCM and the PCM.

What is the purpose of adding butane to gasoline?

Butane is one of the lightest liquid streams that a refinery may create. Four carbon atoms and ten hydrogen atoms make up the butane molecule.

Butane is normally sold as a finished product or blended into gasoline or LPG (in small quantities). Butane is preferred for blending into gasoline because of its high octane, although it is limited by its high vapor pressure. Because of vapor pressure restrictions, butane blending into gasoline is frequently discontinued during the summer months, resulting in a seasonal excess of butane.

Butane is a commercially completed product that is utilized as a home heating fuel, cigarette lighter fluid, refrigerant gas, and propellant, but only in tiny quantities.

Butane is widely transformed to isobutane for use as a feedstock in alkylation processes. Although it is occasionally used as a refinery fuel, this is often its lowest-value end use and should be avoided if possible.

Butane is obtained through a variety of refinery process units as well as external sources such as natural gas facilities (from the separation of NGLs) and steam crackers (in the C4 raffinate).

  • When all crude oil grades are distilled, a little amount of butane is produced. Butane typically exits the distillation tower as a wet gas stream, which is then transferred to a saturated gas plant to be separated from lighter gases (methane and ethane), which are then used as fuel.
  • Large volumes of C4s, particularly saturated butane and unsaturated butylene, are created during the FCC conversion process. Unsaturated olefins are frequently separated and used as feed for the alkylation unit.
  • Coker – The coker conversion process, like the FCC, produces mixed C4s with saturated and unsaturated molecules. However, because the ratio of unsaturated molecules in coker C4s is lower than in FCC, it is less frequent to separate the olefins.
  • Reformer – During the conversion process, reformers will yield about 5% (by volume) of C4s.

What are the components of gasoline blending?

Components for gasoline mixing: naphthas for blending or compounding into final aviation or motor gasoline (e.g., straight-run gasoline, alkylate, reformate, benzene, toluene, andxylene). Oxygenates (alcohols, ethers), butane, and pentanes plus are not included.

What are the many types of gas blends?

One method of displacing petroleum is to mix small volumes of alternative fuel with traditional fuel. E10 (10 percent ethanol/90 percent gasoline), E15 (10.5 percent to 15 percent ethanol combined with gasoline), B5 (5 percent biodiesel/95 percent diesel), and B2 (2 percent biodiesel/98 percent diesel) are examples of low-level fuel blends. Blends can also include two forms of alternative fuels: hydrogen and compressed natural gas (HCNG), which can be a 20 percent hydrogen/80 percent CNG mix. Low-level mixes include B20 (20 percent biodiesel/80 percent diesel) and E85 (51 percent to 83 percent ethanol combined with gasoline, depending on area and season).

Butane is derived from crude oil.

Butane is a colorless, odorless, and shapeless gaseous hydrocarbon that is recovered as a byproduct of crude oil extraction and refining from gas processing plants.

Is butane a type of natural gas?

Propane or natural gas is used to power many furnaces and other appliances. Whether you live in Baltimore, Maryland, Charles Town, West Virginia, or any of the other cities we service, they can keep your house warm and pleasant in the winter.

Natural gas is a mixture of gases that can be found underground, including butane, propane, and methane. It might be a liquid, a compressed or uncompressed gas, or a mixture of the two.

After being extracted from natural gas at a processing facility, propane, also known as liquefied petroleum gas or LPG, is stored as a liquid. Consider the differences between natural gas and propane installation techniques, delivery systems, efficiency, compositions, and safety before deciding which fuel source is ideal for your home.

Butane is a naphtha, right?

Butane is a highly flammable, colorless, and easily liquefied gas that is used in butane lighters and torches. Naphtha is a flammable liquid hydrocarbon combination that is used in wick lighters and burners.

Is butane considered a blendstock?

The addition of blendstock, such as butane, to RFG or regular gasoline would be deemed the manufacturing of gasoline, and the blender would be subject to all RFG and anti-dumping legislation, as well as all standards and procedures that apply to refiners.

Meeting the specifications for RFG or regular gasoline, as well as every-batch sampling, are among these requirements. The solutions to Questions IX-B-5 and -7 can be found in the Question and Answer Document from July 1, 1994. The RFG or conventional gasoline with which the blendstock is blended must be omitted from the blender-compliance refiner’s calculations under 80.65(i) and 80.101(e)(1). In fact, the RFG criteria must be met solely based on the qualities of the blendstock. Under 80.101(i)(1)(i), refiners who make conventional gasoline by blending blendstock with previously-certified conventional gasoline may sample and test the blendstock following each receipt of blendstock to determine compliance with the anti-dumping standards.

Without sampling and testing each batch of butane received, a party who mixes butane into gasoline will be deemed as complying with refiner criteria, provided that:

1) The butane is combined solely with regular gasoline, not with RFG.

2) If butane is blended into gasoline that will be used between May 1 and September 15, the blender-refiner must sample and test the RVP of the gasoline after each time butane is blended, and the results of this testing must be equal to or less than the applicable volatility standard, with no enforcement tolerance applied.

3) The butane blender-refiner acquires specification documents from the butane supplier, which include the butane purity.

a) The butane must be commercial quality, 95 percent pure butane, and meet the contamination levels indicated in the table below, which must be represented in the butane supplier’s documents:

b) Alternatively, the butane must fulfill the contamination levels indicated in the table below, which must be represented in the butane supplier’s documents:

In addition, the blender-refiner must have a quality assurance program that includes sampling and testing the butane obtained from each butane supplier in order to verify the supplier’s specification documentation. Butane sampling and testing must occur once every 65 truck loads of butane, or once every 17 rail cars of butane, received from a butane supplier, or once every three months, whichever comes first. The butane must meet the purity limits stated in the table under this item 3b after analysis of the quality assurance samples.

Butane must be sampled according to ASTM D1265, tested for aromatics, benzene, and olefin levels using ASTM D2163, and sulfur content using ASTM D2784 in order to carry out the quality assurance program.

4) The specification documentation for the butane provider must be based on sampling and testing of the supplier’s stored butane to represent the qualities of the butane provided to the blender-refiner.

5) For a period of five years, the blender-refiner shall keep copies of all butane supplier specification documents, as well as the results of all quality assurance sampling and testing, and make these documents accessible for EPA examination upon request.

6) The blender-refiner may utilize the purity levels stated in item 3 above to include butane in anti-dumping compliance calculations under Section 80.101(g), and may treat butane received in each calendar month as a single, independent batch.


Consolidated List of Reformulated Gasoline and Anti-Dumping Questions and Answers: July 1, 1994 through November 10, 1997 (PDF)

What is blending stock for gasoline?

Blendstock for gasoline refers to a hydrocarbon material that, by itself, does not meet criteria for finished gasoline but can be blended with additional components, such as oxygenates, to generate a blended gasoline that completely meets ASTM or state specifications.

Why does gasoline in different parts of the country have different blends?

Many drivers are likely unaware (or unconcerned) that gasoline is blended differently in the summer and winter. However, thanks to a confrontation in California, where Gov. Jerry Brown wants to allow the use of so-called winter-blend gas earlier in the year in an attempt to lower soaring gas costs in the Golden State, that subject has recently gotten a lot of attention.

The cost of gasoline is a perplexing and intricate subject. But, first and foremost, what exactly is the difference between summer and winter gas? Essentially, winter gas is less expensive, but it is not as pure, and it is bad for the environment.

To meet overlapping state and federal criteria, the United States has around 20 different gasoline blends. The varied classes of gas are used to regulate VOCs (volatile organic compounds), which are more prone to evaporate as the temperature rises. More VOCs equals more smog, especially in the summer, when the heat in the atmosphere increases the propensity for atmospheric ozone, and the VOCs add to the smog intensity.

The various grades of gas are measured using the RVP (Reid Vapor Pressure) system, which is expressed in pounds per square inch (PSI). The easier it is to vaporize a gas blend with a higher RVP number, and the worse it is for the environment. The pressure of all gasoline mixes must be less than 14.7 PSI, which is the usual average air pressure. Any higher than that, and gasoline will turn into a gas.

To keep gas from boiling off in the summer heat, the RVP must be kept as low as possible. For summer-grade fuel, the EPA specifies a maximum RVP of 9.0 PSI to 7.8 PSI, depending on the location (though you get a fudge factor of 1 psi for using gas blended with 10 percent ethanol). For cities like Houston, New York, and Los Angeles, there are even lower RVP-rated fuels. Varying states and towns have different requirements based on seasonal temperaturesWashington state, for example, requires a different type of summer gas than Florida. That is why there are so many different types of blends. To add to the confusion, the period it takes to transition from summer to winter blend gasoline differs by state.

The lower the RVP of a gas blend, the more expensive it is. In the winter, for example, you can mix butane with gasoline, which is relatively plentiful and inexpensive. However, because butane has an RVP of 52, it can’t be used in the summer because it will boil out as a gas. As a result, “purer” summer gasoline is automatically more expensive. (There are also other elements at play.) For example, more people travel in the summer during peak driving season, putting additional strain on demand.)

Returning to California’s problems: First, a fire at a Chevron refinery in August hampered the oil industry’s capacity to satisfy demand, lengthening supply delays and increasing transportation costs. This is especially problematic in California, which has stronger criteria than the rest of the US when it comes to what blends it will sell, leaving it particularly subject to supply shortages.

Brown’s relaxation of the regulations on gas mixes is an attempt to counteract this susceptibility and bring prices down. However, there is no certainty. Despite the fact that gasoline is a commodity, the price-setting system has only a shaky relationship with supply and demand. Rather than having an independent regulating body regulate the supply side of the equation, providers report on their oil supply on a voluntary basis. And we should be suspicious of any numbers that could be manipulated for profit.

What is the distinction between winter-blend and summer-blend gasoline?

Because the gasoline must be able to evaporate at low temperatures for the engine to function correctly, winter-blend gas has a greater RVP. The RVP of summer-blend gas is lower to minimize excessive evaporation when the temperature outdoors rises.