International Newsmaker Q&A: Rex Tillerson

Under the direction of Rex Tillerson, ExxonMobil’s chairman and CEO, the company has addressed a series of questions that you or your customers may have about the key performance, environmental and market factors regarding diesel and gasoline:

Q: How is diesel different from gasoline?

A: While diesel and gasoline are both derived from oil, they work in two different ways and are not interchangeable. Diesel fuel is designed to operate in a diesel engine, where it is injected into compressed, high-temperature air in the combustion chamber and ignites spontaneously. This differs from gasoline, which is ignited in a gasoline engine by the spark plugs.

Q: What is Ultra Low Sulfur Diesel (ULSD)?

A: For model year 2007 (and newer) diesel vehicles, the U.S. Environmental Protection Agency (EPA) mandated the use of ULSD. Very low sulfur fuels reduce particulate emissions and enable the use of advanced aftertreatment devices.

Q: How does a driver know which grade to use?

A: Most engines are designed to operate on ASTM No. 2-D grade, but some diesel engines in stop-and-go service require No. 1-D diesel fuels for the best results. Check the owner’s manual to determine the right fuel for your vehicle and be sure to use ULSD in 2007 model vehicles and newer.

Q: How is diesel fuel better for the environment?

A: Diesel fuel requires less energy to produce than gasoline. It has higher energy density and thus provides better fuel economy.

Q: Why do diesel engines emit smoke?

A: Diesel engine smoke is caused by incomplete combustion. White smoke is caused by tiny droplets of unburned fuel resulting from engine misfiring at low temperature. This smoke should disappear as the engine warms up. Black smoke could be caused by a faulty injector, insufficient air, and overloading and/or over-fueling the engine. Blue-gray smoke is the result of burning lubricating oil and is an indication the engine is in poor mechanical condition.

Q: What factors affect power/fuel economy?

A: Engine design is the most important factor leading to power and fuel economy. However, fuels with a higher density like our Ultra Low Sulfur Diesel No. 2 will provide improved power and fuel economy compared to fuels with Diesel Fuel No. 1 blended into them.

Q: What should be done in the winter to adjust for the cold temperatures?

A: We offer winterized product in a majority of markets that experience severe weather conditions. If temperatures fall well below norms for the local area, or you will be driving much farther north, additional Diesel Fuel No. 1 blending is recommended.

Q: Why shouldn’t a driver just use Diesel Fuel No. 1?

A: While Diesel Fuel No. 1 has an advantage in low temperature conditions, there are some disadvantages, as well. The energy content of Diesel Fuel No. 1 is about 95 percent that of Diesel Fuel No. 2 and will provide a correspondingly lower fuel economy.

Diesel Fuel No. 1 is also lower in viscosity and provides less lubrication for the fuel pump and fuel distributor.

Q: How long can diesel fuel be stored?

A: If you keep it clean, cool and dry, diesel fuel can be stored six months to one year without significant quality degradation. Storage for longer periods can be accomplished through use of periodic filtrations and addition of fuel stabilizers and biocides.

Q: Other than price, what is the difference between regular, midgrade, and premium gasoline?

A: Gasolines are rated based on octane. In most areas of the country our regular gasoline is 87 octane, midgrade is 89 and premium is 91-93. If you check the owner’s manual, you’ll find the recommended level for your engine.

Q: Why should I follow my owner’s manual and choose mid or high-octane fuel? Isn’t gas just gas?

A: To get the best performance out of your vehicle, you should use the octane recommended in your owner’s manual. Most vehicles do not benefit from a higher octane level than what is recommended, but using a lower octane than recommended can cause engine knocking or pinging in some cars.

Q: Does gas have an expiration date?

A: In general, gasoline should be used within a month of purchase. When the engine will not be used for an extended period of time, it’s best to drain the fuel tank and then run the engine until it stalls. If you choose to store gasoline, keep it in a very nearly full, tightly sealed metal container in a cool environment. Be sure to leave some room in the container to allow for some expansion. Under these conditions, the gasoline can be expected to remain of good quality for at least six months.

Q: Is there a situation where the octane my vehicle needs would differ from the level recommended in my owner’s manual?

A: In general, the octane a vehicle needs aligns with the manufacturer’s recommendation. However, each vehicle is different, owing to factors such as manufacturing variability, mileage, type of operation and general condition. As a result, some vehicles may require a higher octane, particularly after an initial period of operation. If knocking or pinging suddenly occurs, using a higher octane grade may resolve the problem.

A small percentage of vehicles may knock because of variations in engines of the same model due to manufacturing tolerances, or because of an unusual build-up of engine deposits. Other factors such as extremely hot weather, changes in altitude or hard driving conditions (like towing a heavy load) may also cause knocking. Many modern vehicles are equipped with an electronic device that detects and eliminates light knocking before you hear it.

Q: Who decides how much gas is going to cost?

A: In most countries with free markets, service station operators – many of whom are independent business people – set retail pump prices. The supplier typically sells the station owner gasoline at a wholesale price reflecting prevailing market conditions. The station operator then decides what price he will charge the public.

When supply exceeds demand, service stations will lower prices to compete with each other for business. When demand exceeds supply, service stations raise prices to prevent run-outs. Higher prices encourage station owners and suppliers to seek additional supplies. This competition generally rebalances supply and demand quickly with minimal disruption to consumers.

Q: What is reformulated gasoline?

A: Reformulated gasoline (RFG) is a special blend designed to reduce harmful automotive emissions. RFG must be marketed in those areas of the United States where air quality doesn’t meet the ozone requirements of the Clean Air Act Amendments. It is formulated to reduce the emissions of NOx and volatile organic compounds, and has lower benzene levels.

Q: What is California Air Resources Board (CARB) gasoline?

A: CARB gasoline is a type of reformulated gasoline designed to reduce emissions. It reduces the emissions of NOx and volatile organic compounds, has lower benzene and sulfur levels, and limits the amounts of aromatic and olefinic compounds in the blends. It is required throughout the State of California.

Q: Do your gasolines contain ethanol?

A: In many areas of the country, oxygenates are required to be part of the gasoline formula. In those areas, our gasolines will contain ethanol, which is an oxygenate. Ethanol is also used in California Cleaner Burning Gasoline and the Reformulated gasolines required in many of the major metropolitan areas of the country. In addition, to meet the Renewable Fuels Standard included as part of the Energy Independence and Security Act of 2007, ethanol blends have been introduced to many more areas of the country.

Q: Does gasoline really need detergents?

A: Yes! Detergents are added to gasoline to help keep vital engine parts clean, including the carburetor or fuel injectors, intake valves and intake port areas. A gasoline detergent is a lot like a household detergent, helping to prevent any harmful deposit buildup.

Gasoline detergents can do such a great job at keeping critical engine components clean that the EPA, through the Clean Air Act, has required them to be added to all gasolines since 1995.

All our gasolines contain effective detergent additives. While the EPA has required all gasolines marketed in the United States to contain detergents since 1995, our gasolines contain significantly more than the minimum quantities required to provide additional protection against fuel system deposits.

Q: What is the importance of a gasoline’s antiknock quality?

A: Antiknock, also known as octane rating, is the measure of a gasoline’s ability to resist knock or ping during combustion. The higher the octane rating, the greater the engine’s resistance to knock or ping. The knocking or pinging in your engine occurs when the air/fuel mixture detonates prematurely. Since it is the gasoline vapor that ignites, the air/fuel mixture must be correct to burn smoothly. Some of the problems associated with knock are overheating of engine parts such as valves, pistons and spark plugs.

Car manufacturers will specify, in the owner’s manual, a minimum octane to be used with their automobiles. Ordinarily, your vehicle will not benefit from using a higher octane than is recommended in the owner’s manual. But if your engine knocks or pings at the recommended octane level, you may need a higher octane gasoline to prevent the knock.

Q: What does a gasoline’s volatility mean?

A: Volatility is the rate at which gasoline vaporizes at a given temperature. The volatility of a gasoline is important because the liquid gasoline must be mixed with air and vaporized in order to burn in the engine.

The volatility characteristics of our gasolines are important to your driving performance. Gasoline with high volatility vaporizes more readily than one with low volatility. In hot weather, gasoline that is too volatile can cause vapor lock and stalling in your vehicle. In cold weather, a gasoline that is not volatile enough may cause hard starting and poor warm-up. In the winter months, for example, a vehicle’s engine is extremely cold before startup, and the gasoline must have a high enough volatility to be able to vaporize easily in a cold engine environment. Our gasoline’s volatility is carefully balanced on a seasonal and geographic basis to provide the correct vaporization characteristics to ensure proper operation in your vehicle.

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