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Types Of Fuel A Chevy Impala Uses (Explained)

This blog seeks to answer the question you pose about a vehicle you might own or are looking to own or just want to get to know better. In answering those questions, we put in a lot of effort and do a lot of research to provide a plethora of information directly or indirectly related to the subject matter.

Introduced in 1958, the Chevy Impala spanned over ten generations. No models were produced between 1986-1999, Impala was reintroduced in 2000 as an eighth-generation sedan, and it remained in production till 2020, with two further generations of the Impala manufactured by GM. In this blog, we will look at the eighth generation (2000-2005), ninth-generation (2006-2016), and tenth-generation (2017-2020) of Impalas.

To comprehensively answer the question regarding what fuel a Chevy Impala takes, we need to have a detailed look at all the available fuel types and the manufacturer’s guidelines as provided in the car owner’s manual. Before we go into the detailed analysis, we provide a summary paragraph below.

Eight engine types were used in the Chevrolet Impala from 2000 until 2020, with the smallest being 2.4L and the largest one 5.3L. Except for engines up to 3.4L, most engines were designed to run on Flex-Fuel (E85). Some engines started as regular gas engines that used 87 octane, but later versions allowed Flex-Fuel also. A few had CNG as a fuel of choice with other options also available – a couple of them were hybrids.

There was a lot of playing around with the engines to attract consumer attention. Still, it also resulted in a lot of confusion regarding what fuel type was the best for a given engine in a particular trim. In the next section, we will try to present a clear picture regarding which fuel type best fits a given engine.

Also read: How Many Miles Can A Chevy Impala Last? (Answered)

Fuel Requirements Based On Engine Type

This section will take a detailed look at the various engines types used between the eighth and tenth generations of Impala and the recommended fuel for each of them.

Eighth generation (2000-2005)

Only three trims were manufactured during the eighth generation with options for 3.4L and two 3.8L, one of which was supercharged. The 3.4L and normal 3.8L engines were designed to run on regular unleaded gas, which has an octane rating of 87, but GM also allows fuel with a higher rating.

For the supercharged version, it was recommended to use premium unleaded gas, any gasoline with an octane rating of 91 or higher. Gasoline with an octane rating of less than 87 can cause engine knocking, which in worse cases can damage your engine.

Cars certified to meet California Emission Standards (see the underhood emission control label) will also operate satisfactorily on fuels meeting federal specifications. However, the emission control system may be compromised, which could, in turn, result in the warranty becoming void.

MMT is not allowed, while fuels with added substances are permitted. In addition, types of gasoline containing oxygenates, such as ethers and ethanol, and reformulated gasoline are also recommended, provided they are within the recommended specification of octane rating.

Ninth generation (2006-2016)

As indicated earlier, most models in this generation are based on Flex-Fuel. However, the 2.4L and 2.5L engines, the 3.9L engines in 2006-07, and the 5.3L engines used in 2006-09 are based on regular unleaded fuel with an octane rating of 87 or greater. In addition, GM allows the use of TopTier Detergent Gasoline in all its vehicles.

If your vehicle’s fuel cap is yellow-colored, then Flex-Fuel or E85 can also be used along with regular unleaded gas. However, Flex-Fuel or any fuel containing more than 15% must not be used in non-Flex-Fuel vehicles. Oxygenated gasoline, containing ethers and ethanol, can be used to comply with the allowed octane rating.

In case TopTier Gasoline is not available, GM recommends using one bottle of Fuel System Treatment PLUS, part number 88861013, added to the fuel tank at every engine oil change. It is the only gasoline additive recommended by General Motors.

MMT is not recommended for use because it affects emission control system performance and reduces spark plug life. Nor is it recommended to use methanol fuel because it can corrode metal parts in the fuel system and damage plastic and rubber parts. Also, it is not recommended to use any detergents in Flex-Fuel or E85 fuel because the damage caused by additives is not covered in the warranty.

To complete the discussion, it should be added that in 2014, GM also introduced two hybrid trims which switched between electric and regular unleaded fuel, and the trim in 2015 that had options for Flex-Fuel, regular unleaded, and Compressed Natural Gas (CNG).

Tenth Generation (2017-2020)

The trend started in 2012 continued in the tenth generation, with all trims having either a 2.5L or 3.6L engine. The recommended fuel for 2.5L is regular unleaded gas with an octane rating of at least 87, while for 3.6L, it is FLex-Fuel. Both can also use TopTier gasoline and oxygenated blends of ether or ethanol, provided that these comply with the recommendations for octane level.

However, Flex-Fuel and blends with ethanol greater than 15% should not be used in 2.5L engines. Two 3.6L trims in 2017 also had options for Compressed Natural Gas besides Flex-Fuel and other recommended fuels noted above. GM does not recommend the use of MMT or detergents in FLex-Fuel, nor does it allow blends with methanol.

What Types Of Gasoline Can And Can’t Be Used?

Beginning in 1970, to meet the stringent EPA emission regulations, car manufacturers looked to produce efficient engines and emission control systems, and petroleum producers invested in producing cleaner and efficient fuels.

As a result, we now have many different fuels available besides conventional fossil fuels and the corresponding engines to run on these other fuels. We will look at some of the different fuels that can power the cars of today, but first of all, let us see what type of fuels are recommended by Chevrolet.

Fuels Recommended by Chevrolet

Chevrolet recommends regular unleaded fuel with an octane rating of 87 or greater, although using premium gasoline would not result in better performance in most cars. Only in a few specific cases does it require premium unleaded gas with a rating of 91 or greater; in that case, lower rating fuels should not be used.

It also advocates the use of TopTier fuel for a cleaner engine and optimum vehicle performance. Flex-Fuel can only be used in engines that are specifically designed for that.

Reformulated Gasoline

The 1990 Clean Air Act mandated Environmental Protection Agency to issue regulations that would require gasoline manufacturers to produce clean-burning gasoline for use in motor vehicles. RFG reduces smog-forming and toxic pollutants in the air we breathe, and now more and more states are implementing regulations for its use.

Gasoline can be formulated in many ways, and the ingredients used to formulate RFG are no different from those used in conventional gasoline. The only difference is in the level at which these ingredients are used in RFG to reduce ingredients that cause air pollution. However, it is also formulated to ensure that RFG meets the power requirements of the vehicles in which it is used.

Although not listed by GM in its list of recommended fuels, RFG can be safely used without any detrimental effects on the engine.

Gasoline / Oxygenated Blends Or E-85

Chemical compounds that have oxygen as part of their molecular structure are called oxygenates. Ethanol is one of the most popular oxygenate used in gas, and a federal mandate requires that all gasoline now sold in the USA be oxygenated. Therefore regular unleaded gas has an ethanol content of up to 10 percent and is also called E10.

On the other end of the spectrum is E85 or Flex-Fuel that is 85% ethanol and 15% gasoline. The majority of Impalas manufactured between 2000 and 2020 can be run on Flex-Fuel. One needs to consider the pros and cons when using E85 which are listed below.


  • Eco-friendly with lower emissions.
  • Burns whatever mixture is present in the combustion chamber of the vehicle.
  • Can potentially be produced from waste materials.


  • Reduction in miles per gallon.
  • Since ethanol is sourced from certain crops, it can lead to shortage and price increase of such crops.
  • Causes engine corrosion.
  • When the ambient temperature is above 90° F (32° C), the car experiences hard starting and rough idle following startup even if the above recommendations are followed.

If your car’s fuel cap is yellow-colored, then it is safe to use Flex-Fuel. Do not use Flex-Fuel in cars not manufactured to run on it.

Gasoline With Added Materials

Some of the reasons for adding gasoline materials are increasing octane rating, reducing engine corrosion, or acting as lubricants. Added materials in gasoline allow for higher compression ratios which means that the engine can extract more energy from combustion.

There is a long list of materials that are added or can be added to gasoline, but not all are useful and hence not recommended to be used in gasoline. GM only recommends the use of TopTier gasoline in its vehicles.

If TopTier is not available in your area, GM suggests using one bottle of Fuel System Treatment PLUS, part number 88861013, added to the fuel tank at every engine oil change. It is the only external gasoline additive recommended by General Motors.

Gasoline With MMT

MMT or Methylcyclopentadienyl manganese tricarbonyl is used as an octane enhancer in gasoline produced by Afon Chemicals. MMT is allowed in US gasoline at a level equivalent to 1/32 grams per gallon of manganese.

MMT has been shown to cause several issues, such as plugging of monolithic converters, increased hydrocarbon emissions, and excessive spark plug deposits.

MMT seems to have more downsides than any substantial advantage and hence not recommended by car manufacturers, including Chevrolet. The following is taken from the Impala owner manual.

Some types of gasoline, mainly high octane racing ones, can contain an octane-enhancing additive called methylcyclopentadienyl manganese tricarbonyl (MMT). Do not use types of gasoline and/or fuel additives with MMT as they can reduce spark plug life and affect emission control system performance. The malfunction indicator lamp may turn on. If this occurs, see your dealer for service. (source)


Biodiesel is an alternate form of fuel similar to fossil diesel produced from vegetable oil, animal fats, grease, waste cooking oil. It is usually used as a blend with fossil diesel, and 5% biodiesel mixed with fossil diesel has shown to have good fuel economy and lower emissions. None of the impalas was manufactured with a diesel engine.

Also read: What Is The Oil Type, Capacity, And Weight Of A Chevy Impala?

What If I Hear A Knocking Noise From The Engine After Refilling

Knocking is caused by using gas of inferior quality, which in the case of Impala, is gas with an octane rating less than 87 for regular unleaded or less than 91 for premium gas.

It is caused by uneven burning of fuel in engine cylinders.

With the correct balance of air and fuel mixture, fuel burns in small regulated portions rather than all at once. Each part ignites the next one and so on. Engine knock takes place due to uneven burning, and the ignition of the following pockets takes place at the wrong time, which results in the annoying loud knocking sound.

If you hear a knocking sound immediately after filling your gas tank, then you need to use better quality gas or gas with recommended detergents such as TopTier. However, if the sound does not go away even on using better quality gas or gets louder, you are advised to refer to a qualified motor mechanic. Failure to do so may result in your warranty becoming void.

Also read: Chevy Impala Transmissions: Overview, Problems, Fluids

Does the Chevy Impala Have Good Gas Mileage?

In this section, we tabulate the fuel economy data for the various Impala versions. We will provide MPG data for the city, highway, and combined. The combined MPG is a weighted average of 55% of city MPG and 45% of highway MPG.

Eighth generation

YearEngine LFuelMPG CityMPG HighwayCombined MPG
20003.4Reg Unl172921
20003.8Reg Unl172721
20013.4Reg Unl192922
20013.8Reg Unl172821
2002-053.4Reg Unl192922
2002-053.8Reg Unl172620
2004-053.8 SCReg Unl162620

Ninth generation

YearEngine LFuelMPG CityMPG HighwayCombined MPG
20063.5Reg Unl182822
20063.9Reg Unl172520
20065.3Prm Unl162619
20073.5Reg Unl182822
20073.9Reg Unl182621
20075.3Prm Unl162419
20083.5Reg Unl182922
20083.9Reg Unl182821
20085.3Prm Unl162419
20093.5Reg Unl192923
20093.9Reg Unl172721
20095.3Reg Unl162419
20103.5Reg Unl182922
20103.9Reg Unl172721
20113.5Reg Unl192923
20113.9Reg Unl172621
20123.6Reg Unl182922
20133.6Reg Unl182922
20142.4Reg Unl243528
20142.5Reg Unl213124
20153.6Reg Unl192822
20153.6Reg Unl182922
20153.6Reg Unl182821
20162.5Reg Unl223125
20163.6Reg Unl192822
20163.6Reg Unl182821
20163.6Reg Unl172520

Tenth generation

YearEngine LFuelMPG CityMPG HighwayCombined MPG
20172.5Reg Unl223025
20173.6Reg Unl192822
20173.6Reg Unl182822
20182.5Reg Unl223025
20183.6Reg Unl192822
20183.6Reg Unl182822
20192.5Reg Unl223025
20193.6Reg Unl192822
20193.6Reg Unl182822
20203.6Reg Unl192822

What’s The Gas Tank Size Of A Chevy Impala?

The tank size for all models from 2000-2013 is 17 gallons. From 2014-2020 all models had a tank size of 18.5 gallons except for the 2014 hybrid trims with a tank size of 15.8 gallons.

How Much Does It Cost To Fill Up A Chevy Impala

Fuel prices vary significantly from state to state in the USA. For example, it costs $4.388 a gallon in California, $2.816 a gallon in oil-rich Texas. The average cost of a gallon in the USA as of 11th October 2021 is $3.36 to a gallon. The table below gives you an idea of the cost of filling in the high, low, and average end of the gas price spectrum.

Tank sizeCost to fill @4.388 / galCost to fill @$2.816 / galCost to fill @3.36 / gal

Also read: The Exact Bolt Pattern Of A Chevy Impala