Car Care FAQs

To help you learn more about gasoline, we have assembled a collection of the most frequently asked questions, all answered by our Fuel Experts. Browse by topic to find the answers.


Q. What is gasoline?
A. Gasoline is the fuel designed for spark-ignition internal combustion engines. Conventional gasoline is a mixture of compounds, called hydrocarbons, derived from petroleum crude plus a small amount of a few additives to improve its stability, control deposit formation in engines, and modify other characteristics. Most gasoline sold in the US today contains up to 10% ethanol.

Q. All the major oil companies say that their gasoline is great. Why should I buy Chevron gasoline?
A. All Chevron-branded gasolines contain the unique Techron additive. Techron contains a polyerther amine (PEA)-based chemistry designed to keep vital engine parts clean and remove deposits left by lower quality gasolines, while minimizing any contribution to harmful combustion chamber deposits. Chevron with Techron was also the first gasoline to be designated as a TOP TIER Detergent Gasoline by BMW, General Motors, Honda and Toyota in the US and Canada.

Q. Why should I buy Chevron gasoline over lower quality gasolines?
A. Lower quality gasolines can leave harmful deposits in your car's engine. As these deposits accumulate over time, your car may begin to hesitate and stumble during acceleration, knock or lose power. Chevron with Techron is unbeatable at cleaning up your engine, which can reduce emissions, restore lost power and performance, and keep your engine clean. There's no better gasoline for you to help protect your engine's performance than Chevron with Techron.

Q. I already buy premium gasoline. Why should I buy Chevron Supreme® instead of my current brand?
A. Deposits on fuel injectors, intake valves and combustion chambers can cause your car to produce higher emissions, which contribute to air pollution. Chevron Supreme with Techron is unbeatable at cleaning up the intake systems and avoiding these deposits, giving you reduced emissions compared to lower quality premium gasolines. All Chevron branded gasolines contain the unique Techron additive. Techron contains a polyether amine (PEA)-based chemistry, designed to clean up intake system deposits while minimizing any contribution to harmful combustion chamber deposits that may increase emissions or lead to deposit-related engine knock or power loss.

Chevron with Techron

Q. What is Techron?
A. Techron is a fuel additive that acts as a detergent to help keep your engine clean. Techron uses polyether amines (PEA) to help fight deposits in an engine's intake system and minimize contribution to harmful combustion chamber deposits. Over 30 years ago, after discovering that PEAs made effective deposit control additives, Chevron patented them and has been reformulating and improving Techron ever since.

Q. What makes Chevron with Techron special?
A. Many other gasolines use a detergent additive that's based on polybutene amine (PBA) chemistry. PBA-based additives do an adequate job of controlling intake system deposits-but only if the dosage in the fuel is high enough to do the job. In recent years, the concentration of PBA in many gasolines has fallen so low that the gasolines do not keep intake systems clean. And if a gasoline uses a concentration of PBA-based additive that's high enough to keep the intake system clean, the additive itself can contribute materially to combustion chamber deposits. Excessive combustion chamber deposits can cause an engine to need a higher octane gasoline to avoid knock or loss in performance. These excessive deposits can also cause higher tailpipe emissions. In contrast, Chevron's unique deposit control additive, Techron, provides unsurpassed intake system deposit control, while simultaneously minimizing any contribution to harmful combustion chamber deposits.

Q. I was told that Chevron has the Techron additive in all grades of gasoline? Is this true? I thought it was only in the Supreme grades.
A. It's true. All grades of Chevron gasoline contain a highly effective amount of Techron, so no matter which grade your car takes, it's getting the quality and unsurpassed cleaning power of Chevron with Techron.

Additives with Techron

Q. Do I need to add a bottle of deposit control additive such as Techron® Concentrate Plus to the gasoline in my fuel tank?
A. If you regularly use a high-quality gasoline such as Chevron, you probably don't need Techron Concentrate Plus. However, if you have an engine that is sensitive to deposit formation, or if your vehicle is regularly used under severe conditions, you may also benefit from using Techron Concentrate Plus.

Q. What is the difference between Chevron with Techron at the pump and Techron Concentrate Plus in the bottle?
A. The principal difference is additive concentration and rate of deposit clean-up. Chevron gasolines with Techron over multiple fill-ups will help clean deposits on intake valves and minimize harmful combustion chambers deposits. When added to a full tank of gasoline, a bottle of Techron Concentrate Plus results in an additive concentration roughly 10 times stronger. This mega-dose of Techron provides a much quicker clean up of intake valve deposits left by lower quality gasolines. In addition, the high concentration of Techron reduces combustion chamber deposits, which can help eliminate deposit-related engine knock or power loss.

Q. Is Techron just a more diluted version of Techron Concentrate Plus?
A. No. While both use a polyether amine-based chemistry, each is optimized for its particular application. Chevron with Techron helps clean engine deposits left by low quality gasolines and helps keep engines clean through regular use, while Techron Concentrate Plus provides a quicker clean-up of deposits left by lower-quality gasoline through a higher additive dose optimized for fast cleanup.

Q. My car is knocking and pinging. What is causing this? Can Techron Concentrate Plus help?
A. Knocking and pinging is generally caused by improper combustion in your engine, called “auto-ignition.” If the gasoline-air mixture auto-ignites somewhere in the cylinder (other than at the spark plug) just after spark ignition, the auto-ignition combustion wave can interact with the spark-initiated combustion wave, causing the vibration we hear as knock or ping. Increasing engine load, temperature, compression, spark-advance, air-fuel ratio and combustion chamber deposits all increase the tendency for an engine to knock. Using higher octane gasoline reduces an engine's tendency to knock. If excessive combustion chamber deposits are contributing to the knocking problem, you may benefit from adding a bottle of Techron Concentrate Plus to your next tank of gasoline.


Q. The gasoline pumps at my Chevron station say that the gasoline is oxygenated during the winter to reduce carbon monoxide emissions. What does oxygenated mean and why is this required?
A. Oxygenated gasoline is a mixture of conventional gasoline and one or more combustible liquids which contain oxygen. At present, ethanol is used in the United States. The government requires gasoline to be oxygenated during the winter in areas that have a carbon monoxide pollution problem (cold weather and atmospheric inversions worsen carbon monoxide pollution). Oxygenated gasoline helps engines run leaner, which helps some engines – particularly older engines – produce less carbon monoxide.

Q. Why Oxygenated Gasoline?
A. Oxygenated gasoline can reduces carbon monoxide emissions in some vehicles under certain operating conditions. Engines emit more carbon monoxide when they are fed rich air/fuel mixtures — mixtures with more fuel than oxygen in the mixture. Rich air/fuel mixtures are used during engine startup and warm-up and at full throttle. Oxygenated gasoline requires less oxygen (from the air) for complete burning than the same volume of conventional gasoline.

Q. What oxygenates does Chevron use for oxygenated and reformulated gasoline?
A. Chevron only uses ethanol in its oxygenated gasolines.

Q. Will using oxygenated gasoline reduce my gas mileage?
A. Oxygenated gasoline reduces fuel economy an average of 2 to 3 percent because oxygenated gasoline contains less energy than non-oxygenated gasoline. Many other factors can impact mileage far more than oxygenated gasoline. Things like:

  • How well your car is maintained
  • How fast you drive
  • Traffic congestion
  • Rain and snow, cold weather, and tire pressure

Q. Can I use oxygenated gasoline in my lawnmower? How about my boat?
A. Our survey of the manufacturers of engines for non-automotive uses — boats, garden tools, chain saws and snowmobiles — indicates that oxygenated gasoline will perform satisfactorily in most later-model engines. However, some manufacturers expressed concerns about its use in older engines. The owner's manual is the most authoritative source of information about the fuel requirements of your equipment. If your equipment is older and the manual does not mention oxygenated gasoline, consult an authorized dealer.

Q. What is Ethanol?
A. Ethanol is ethyl alcohol or grain alcohol, mainly produced in the Midwestern United States from corn stock. It can be used as a biofuel alternative to gasoline - known as E85 or "ethanol fuel" which contains more than 50% ethanol - in "flex fuel" engines, but it's primary use in the U.S. is as an oxygenate. As an oxygenate, its mixture is 10 percent or less ethanol in finished gasoline. In some areas of the US, fuel marketers offer fuels which contain greater than 10 percent ethanol, but less than 50%. These fuels should only be used in "flex fuel" engines and vehicles.

Q. It seems like the dispensers at every retail station I go to has a "contains ethanol" decal on it. Why is this?
A. The Energy Independence and Security Act (EISA), which became federal law in 2007, mandates increasing use of "renewable" fuels. The amount of renewable fuel that needs to be sold increases annually. Currently, blending ethanol into gasoline is the primary means by which this mandate is being met.

Octane and Knocking

Q. What is octane?
A. Octane, or Octane number, reflects a gasoline's antiknock quality. It's a measure of the ability of gasoline to resist knocking when it is burned in an engine. Laboratory testing that determines a gasoline's octane number involves burning the fuel in a single-cylinder engine under different conditions to yield a Research octane number (RON) and a Motor octane number (MON). The octane number posted on U.S. gasoline dispensers in service stations is the antiknock index (AKI) - the average of RON and MON [(RON + MON)/2, usually abbreviated (R + M)/2]. The AKI was chosen as the posted value in the U.S. because it proved to be the best indicator of the antiknock performance of gasoline in the majority of U.S. vehicles. In other parts of the world, RONs are frequently posted on gasoline pumps.

Q. My car owner's manual says that I can use regular unleaded gasoline. Is it true that a car engine's octane requirements can increase over time?
A. Yes, and Chevron Supreme and Plus gasolines have high octane that can help maximize performance in cars with increased octane number requirements. Over time, deposits can accumulate in your car's combustion chambers. These deposits can cause knocking and pinging, or reduced performance, particularly if your car has driven over 15,000 miles. A higher octane number gasoline can help you reduce or eliminate these problems by improving your engine's combustion process. While some of these engines may be satisfied by the octane offered by our Plus grade, others may require the even higher octane of Chevron Supreme. So if combustion chamber deposit build-up is affecting your car, Chevron Plus and Supreme with Techron can help.

Q. Can knocking harm my engine?
A. Occasional light knocking won't harm an engine. Heavy or prolonged knocking can result in a loss of power, overheating of parts in the cylinder and engine damage. Techron Concentrate Plus has been proven to help deposit clean-up for fuel injectors, ports and intake valves and combustion chambers. It actually helps restore performance lost due to deposit build-up.

Q. How can I stop my vehicle from knocking?
A. Have a mechanic determine whether your engine is in tune and the emissions control system is functioning properly. If it is, then there are two courses of action.

  • Use a gasoline with a higher antiknock index (AKI)
  • Treat the gasoline with a bottle of Techron Concentrate Plus. If there are combustion chamber deposits in the engine, the treatment will reduce them, which, in turn, may lower the octane number requirement of the engine. This may decrease the engine's tendency to knock until these deposits reform.

Q. How much octane do you need?
A. If you have an older car or a high performance car, you may need a higher octane gasoline to help prevent engine knocking.

Your driving conditions can increase your car's octane requirements. For example:

  • Do you make a lot of short trips?
  • Do you drive in high temperatures?
  • Do you carry or pull heavy loads?
  • Do you drive in a low altitude area?

If you answered yes to any of the above, your vehicle may perform better with a higher grade of Chevron with Techron. If your engine is knocking or losing power on a lower octane fuel, in most cases, switching to a higher octane fuel can help.

Q. What octane gasoline should I use in my vehicle?
A. For starters, use a gasoline with the octane number (AKI) recommended by your owner's manual. Using gasoline with an antiknock rating higher than that required to prevent knock will not improve a vehicle's performance, including its power, unless the vehicle is equipped with a knock sensor and the car's computer is controlling the engine to reduce or eliminate knock on the lower octane grade fuels. Many late model high-performance engines fall into this category.

There are two reasons why your vehicle might knock on a gasoline with the AKI recommended by the owner's manual:

  • The engine is at the upper end of the octane number requirement range.
  • Combustion chamber deposits in your engine are higher than usual.

Q. What will happen if I use the wrong octane gasoline in my vehicle?
A. Using a gasoline with an AKI lower than required by your vehicle can cause the engine to knock or lose power. If the engine is equipped with a knock sensor and the car's computer is controlling the engine to reduce or eliminate knock, using a gasoline with an AKI lower than that required by your vehicle will decrease the vehicle's power and acceleration. Using a gasoline with an AKI higher than that required by your vehicle will not improve its operation.

Q. What determines my car's octane requirements?
A. Your car's octane requirements are mainly determined by its basic design. In addition, variations in engines due to manufacturing tolerances can cause cars of the same model to require a different octane of several numbers. Also, as a new car is driven, its octane requirement can increase because of the buildup of combustion chamber deposits. This continues until a stable level is reached, typically after about 15,000 miles. The stabilized octane requirement may be 3-6 numbers higher than when the car was new. Premium or mid-grade fuel may be advisable to prevent knock or loss of power.

Other factors also influence your car's knocking characteristics:

  • Temperature - Generally, the hotter the ambient air and engine coolant, the greater the octane requirement.
  • Altitude - The higher the altitude above sea level, the lower the octane requirement. However, modern computer-controlled engines adjust spark timing and air-fuel ratio to compensate for altitude changes, and thus the effect of altitude on octane requirement is smaller in these vehicles.
  • Humidity - The drier the air, the greater the octane requirement. The recommendations that vehicle manufacturers give are for normal- to low-humidity levels.
  • Engine spark timing - Octane requirements increase as spark timing is advanced. Both the basic setting of the spark timing and the operation of the automatic spark advance mechanisms are important in controlling knock. In some computer controlled engines, the spark timing can only be changed by replacing modules in the computer. If they are equipped with knock sensors, these computer controlled engines have the ability to retard the ignition temporarily when a sensor detects knock. This temporarily reduces the octane requirement and may also temporarily reduce vehicle performance.
  • Method of driving - Rapid acceleration and heavy loading, such as pulling a trailer or climbing a hill, may result in a greater octane requirement. Stop-and-go driving and excessive idling can increase octane requirements by causing the buildup of combustion chamber deposits.
  • Malfunctions of emission control systems - An improperly functioning emissions control system can affect the octane requirement by changing the air-fuel mixture or by not providing dilution gases through the exhaust gas recirculation (EGR) system. If a malfunction occurs, your vehicle should be taken to a qualified vehicle service mechanic. Some problems are indicated by warning lights on the driver's instrument panel.

Fuel Economy

Q. What can I do to get better fuel economy?
A. Good fuel economy is a combination of good vehicle maintenance and sensible driving. Maintenance factors which contribute to good fuel economy are:

  • A properly tuned engine
  • A clean air filter
  • Aligned and balanced front wheels
  • Tires with the correct air pressure

Mistuned engines also result in higher emissions. The onboard diagnostic system in a modern car will alert you to an engine problem.

Sensible driving involves:

  • Smooth, steady acceleration rather than jackrabbit starts
  • Driving at moderate rather than high speeds on the highway
  • Not carrying a heavy load using a luggage rack, or towing a trailer unnecessarily
  • Not using the air conditioner or defroster excessively
  • Not idling the engine when it could be turned off

Some factors which reduce fuel economy are beyond your control: water, slush, or snow on the road, head winds, driving up hill, and driving in stop-and-go traffic.

Filling and Storing Gasoline

Q. What are the guidelines for storing gasoline?
A. Chevron gasoline can be stored for a year without deterioration when the storage conditions are good — a tightly closed container, moderate temperatures, and out of direct sunlight.

Chevron recommends that gasoline not be stored unnecessarily. A supply that won't be needed for several months should be used and replenished when the need reoccurs.

Q. What are the guidelines for filling a gasoline container?
A. Below are the guidelines that are recommended for filling a gasoline container:

  • Use only an approved portable container (1 to 5 gallons, metal or UL approved plastic, colored red). The container must be in good condition with a vapor-tight cap. Never store gasoline in glass or unapproved containers.
  • When filling container, follow same rules as when fueling car: turn off engine; extinguish smoking materials, leave electronic devices in the vehicle.
  • Place the portable fuel container on the ground during filling, and keep the metal nozzle spout in contact with the container to prevent build up and discharge of static electricity. Never fill a container in the bed of a pickup, in the back of a station wagon, or in the trunk of a car.
  • Keep container five feet away from cars to prevent ignition of fumes by hot engines or mufflers. Ask others, particularly children, to stand back during filling.
  • Manually control the nozzle valve throughout the filling process. Fill a portable container slowly to decrease the chance of static electricity buildup and minimize spilling or splattering.
  • Back off on the trigger to slow fuel flow as the container becomes full. Fill container no more than 95 percent full to allow for expansion. When filling is complete, tightly cap container. Wipe off any gasoline that spilled on the outside of the container. Ask the station attendant to properly dispose of the material used to wipe off the gasoline.

Q. Can static electricity really be enough to ignite gasoline?
A. Yes, but static electricity-related incidents at retail gasoline outlets can be avoided. In the unlikely event a fire occurs when refueling, leave the nozzle in the fill pipe and back away from the vehicle. Notify the station attendant immediately so that all dispensing devices and pumps can be shut off with emergency controls. Use the emergency shutdown button to shut off the pump.

Safety tips to avoid static electricity buildup:

  • Upon exiting vehicle and before handling the nozzle or fuel door, always touch a metal part of the vehicle such as the door or hood.
  • To avoid a build-up of static electricity, do not get back into your vehicle during refueling.
  • If you cannot avoid getting back into the vehicle, upon exiting always touch a metal part of the vehicle away from the fill point before handling the nozzle.

To minimize the danger from fire while filling a portable container with gasoline:

  • Turn off your vehicle's engine.
  • Extinguish smoking materials (cigarettes, pipes, etc.).
  • Remove the container from the vehicle and place it on the ground a safe distance from the vehicle.
  • Keep the nozzle in contact with the container at the inlet during fuel transfer.


Q. I've heard some talk about "nitrogen-enriched" gasoline. Can you tell me what nitrogen in gasoline does?
A. The reference to "nitrogen-enriched" motor gasoline has to do with the deposit control additive that is required by federal law to be used in the gasoline. All commercial deposit control additives, which can help control deposits in injectors or carburetors and on intake valves and intake ports, contain nitrogen. Nitrogen enrichment is nothing new. But, nitrogen alone does not provide the engine keep-clean and cleanup necessary to help with good performance, maximizing fuel economy, and keeping emissions low. The basic polymer in the deposit control molecule also plays an important role. The molecular structure of polymer also can affect the amount of combustion chamber deposits that form and possibly affect intake valve sticking. Some deposit control additives contain several components to optimize performance. The concentration of the deposit control additive in the gasoline is another critical factor. So, just promoting nitrogen enrichment doesn't provide a meaningful assessment of a deposit control additives performance.

Direct Injection Engines

Q. What are direct injection spark ignition engines?
A. Direct Injection Spark Ignition (DISI) engines are the latest advancement in gasoline engine technology, which can offer greater fuel efficiency and power when compared to conventional Port Fuel Injection (PFI) engines. Increasing fuel efficiency is a key means of reducing CO2, a greenhouse gas emission. In conventional engines, fuel is injected into the intake ports of each cylinder. Deposits formed in the combustion chamber can increase the octane appetite of an engine and increase emissions of nitrogen oxides. The PEA-based chemistry of Techron is known to be effective in controlling these combustion chamber deposits. All of this adds up to a fuel that is great for DISI engines.

Q. Do you expect all grades of Chevron gasoline with Techron to perform similarly in direct injection engines?
A. The cleaning performance of Chevron with the Techron additive is strong in all grades of gasoline. However, we recommend using the grade of gasoline recommended by the manufacturer.

Q. Will Chevron gasolines with Techron help direct injection engines meet emissions requirements?
A. Based on our knowledge of how the polyether amine (PEA)-based chemistry in Techron technology behaves, and based on preliminary test results, we believe Techron will be helpful in controlling emissions in direct injection engines, like it is in conventional engines.

Regional Fuels

Q. What is CARB Diesel?
A. Beginning in October 1993; CARB implemented a 10 volume percent limit on the aromatics content of vehicular diesel fuel as a means to achieve further reductions in diesel engine particulate matter (PM) and nitrous oxide (NOx) emissions. Subsequent to the implementation of the 10 volume percent aromatics limit, CARB adopted a provision for alternative low aromatics diesel (ALAD) formulations, whereby a refiner/producer could apply for certification to produce an alternative diesel fuel formulation if they could demonstrate through a specified testing protocol that their formulation provided equivalent or better emissions performance when compared to a 10 volume percent aromatics reference fuel. Most diesel fuel in California today is produced to a certified ALAD formula.

Q. What is TxLED?
A. TxLED fuel is a low emissions diesel fuel regulated by the state of Texas. It is similar to CARB-diesel fuel, with one additional specification. Like California, Texas requires that TxLED have an aromatics content no greater than 10 volume percent. In addition, Texas requires a minimum cetane number of 48. The alternative low aromatics diesel (ALAD) formulations that have been certified by CARB are also acceptable for TxLED. In addition, Texas has protocols whereby alternative formulations that provide equivalent emissions benefits to LED can be certified. TxLED is required to be used in both on-highway vehicles and in non-road agricultural and construction equipment.

General Information on Diesel Fuel

Q. What are the general specifications that define a diesel fuel in the U.S.?
A. The basic specification for diesel fuels used by the petroleum industry and adopted by many U.S. states is ASTM International Standard D975. D975 includes a variety of property limits selected to ensure that finished fuels will provide acceptable performance for the majority of users.

Ultra Low Sulfur Diesel (ULSD)

Q. What is S15 (ULSD)?
A. S15 (ULSD) is defined by the U.S. Environmental Protection Agency (EPA) as U.S. diesel fuel with a sulfur content not to exceed 15 ppm (parts per million). S15, S500, and S5000 are designations for diesel fuels that meet 15 ppm, 500 ppm, and 5,000 ppm maximum sulfur content, respectively, as defined in the ASTM International standard D975 Table 1. In different regions of the world ULSD may refer to different maximum sulfur content values, but ULSD and S15 are often used interchangeably in North America (U.S. and Canada).

For additional information on the S15 (ULSD) regulations visit the
Clean Diesel Fuel Alliance Information Center (

Q. Where can I get additional information on S15 (ULSD)?
A. The U.S. Environmental Protection Agency (EPA) web site ( has information covering all aspects of the Clean Diesel and S15 (ULSD) program.

The Clean Diesel Fuel Alliance ( is a group of public and private organizations that came together to help facilitate the introduction of S15 (ULSD).

Find Your Station

The science and history behind Techron: Discover Chevron's unique fuel additive. Learn more