Types Of Gas An Audi A6 Takes (Explained)

The Audi A6 is a mid-size luxury sedan that offers great competition for the BMW 5-series and the Mercedes E-class. At a starting price of more than $55,000.00, it is by no means a cheap car. Let us take an in-depth look at the available engines for the Audi A6 and how it performs gas-wise.

For all generations of the A6, Audi recommends using premium unleaded gasoline with 91 octane for optimum performance. However, most generations (except the second generation) can also use 87 octane when 91 octane is unavailable. The A6 with a diesel engine uses ultra-low sulfur diesel number 2.

We have seen from experience that using premium octane-grade fuels yields better engine performance and most Audi vehicles are made with this in mind including the Q8 and Q3. However, that certainly doesn’t tell the fuel story. Below, we’ll dive deeper into the fuel requirements for different generations, fuel economy, and much more. Read on!

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Does The Audi A6 Require Premium Gasoline?

2018 – Present

The latest generation of the Audi A6 is offered with two types of engines, a 2.0-liter inline four-cylinder and a 3.0-liter 6-cylinder engine. This is similar to the closely related A7 as well.

For both of these engines, Audi recommends fuels with a minimum octane grade of 87. However, 91 octane is recommended at all times for optimum performance and longevity of the engine.

Engine	Fuel Requirement
3.0-liter 6-cylinder	87-octane minimum, 91 recommended
2.0-liter 4-cylinder	87-octane minimum, 91 recommended

2011-2018

Audi A4’s 4th generation had four gasoline and one diesel engine. The diesel engine displaces at 3.0 liters, and Audi suggests that the ultra-low sulfur diesel number 2 should be used for this engine.

The gasoline engines had a 2.0-liter 4-cylinder base variant. The 6-cylinder engines had 3.0, and 3.2-liter displacements. 87-octane is the absolute minimum, whereas 91-octane is recommended for optimum performance.

Engine	Fuel Requirement
3.2-liter 6-cylinder	87-octane minimum, 91 recommended
3.0-liter 6-cylinder	87-octane minimum, 91 recommended
2.0-liter 4-cylinder	87-octane minimum, 91 recommended
3.0-liter 6-cylinder diesel	ULSD Number 2

2004-2011

For the 3rd generation of Audi A6, there were five different displacements. Starting with a 2.7-liter base variant and including 3.0, 3.1, 3.2, and 4.2-liter engines. Again, 87-octane is the absolute minimum, whereas 91-octane is definitely recommended.

Engine	Fuel Requirement
4.2-liter 8-cylinder	87-octane minimum, 91 recommended
3.2-liter 6-cylinder	87-octane minimum, 91 recommended
3.1-liter 6-cylinder	87-octane minimum, 91 recommended
3.0-liter 6-cylinder	87-octane minimum, 91 recommended
2.7-liter 6-cylinder	87-octane minimum, 91 recommended

1997-2004

Audi A6’s 2nd generation was offered four engine sizes — from 2.7-liter to 2.8-liter and 3.0-liter engines with a 6-cylinder set-up. An 8-cylinder, 4.2-liter engine was also offered. For all of these engines, Audi recommends using fuels with a minimum octane rating of 91.

Engine	Fuel Requirement
4.2-liter 8-cylinder	91-grade octane minimum
3.0-liter 6-cylinder	91-grade octane minimum
2.8-liter 6-cylinder	91-grade octane minimum
2.7-liter 6-cylinder	91-grade octane minimum

1994-1997

A 2.8-liter 6-cylinder engine was Audi’s only option with the A6. Audi recommends using fuels with a minimum octane grade of 87. However, 91 is recommended for optimum performance.

Engine	Fuel Requirement
2.8-liter 6-cylinder	87-octane minimum, 91 recommended

If you’re interested in the different gasoline requirements for all Audis, please read the article we just linked.

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

In today’s world, many different types of fuels are available to choose from. Let’s see how these fuel types stack up in light of Audi’s recommendations for or against them for the A6.

Reformulated Gasoline

With a focus on the environment, engineers have successfully offered various gasoline products for sale that are environmentally friendly. One such type of gasoline is RFG or reformulated gasoline. RFG is environmentally friendly as it burns cleaner and greener than regular gasoline.

Given the environment-friendliness of RFG, one might expect some suggestions from Audi. But Audi remains neutral by neither suggesting for nor against using RFG. However, from experience, we know that carmakers recommend reformulated gasoline whenever possible.

Audi, as we’ve also mentioned in the Audi A3 fuel type or the Audi A5 fuel type, even the Audi Q3 fuel type, doesn’t explicitly recommend reformulated gasoline in the owner’s manuals because it’s a German brand, and RFG doesn’t exist in Europe.

Gasoline/Oxygenated Blends Or E-85

Oxygenated gasoline blends are types of gasoline blended with a certain amount of ethanol or methanol. These chemicals are mainly helpful during winter when temperatures drop lower and lower. This provides a more difficult starting point for the engine. Ethanol and methanol help the engine start more quickly.

However, you can’t get just ethanol or methanol whenever you please. These chemicals are pretty dangerous for the engine and the fuel system, and using them should be done by following these rules:

• Never use fuel that contains more than 3% methanol in any generation of the A6.
• Only use fuel that contains a maximum of 15% ethanol for A6 made from 2015 onwards. A6 made before 2015 (up until 2014) can take a maximum of 10% ethanol.

Gasoline With Added Materials

Gasoline may be added with different materials for different purposes. Some additives are cleaning agents, and some are detergents available today at various gas stations.

However, it’s good to know that Audi strongly advises against using additives in your A6. This is because these additives can contain materials such as silicon or metallics that will seriously damage the engine and the fuel system.

Therefore, it’s recommended that you buy fuel that already has all the proper additives mixed into it. This kind of fuel can be purchased at certified TOP TIER gasoline retailers. These retailers sell gasoline that will provide the optimal performance for your engine and clean it as well as possible without damaging it. You can find a retailer at toptiergas.com.

Gasoline With MMT or MTBE

MMT, which is Methylcyclopentadienyl Manganese Tricarbonyl, is an octane enhancer. It was sold as a supplement when it was introduced, but later on, it was sold as an octane enhancer. MTBE is also an available octane enhancer.

Although Audi stays silent about using MMT with gasoline for MTBE, it suggests that one may use it but should keep the below points in account. These are:

• Fuels with a minimum octane rating of 87 should be used
• MTBE blend should not be in a proportion higher than 15%

Biodiesel

Biodiesel is a nature-friendly diesel fuel obtained from processed restaurant grease, animal fat, and other sources such as vegetable oils. This type of diesel is quite friendly in terms of its environmental impact. We have tried to determine if Audi suggests in favor or against the use of biodiesel, but the owner manuals for Audi A6 don’t state anything.

However, they say that biodiesels with concentrations higher than 5%, like B11, B20, and B100, are strictly prohibited.

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

Engine knocking can be caused by using fuels with lower octane grades than recommended. In the case of the Audi A6, it is associated with fuels at an octane rating lower than 87. This knocking sound is also known as spark knock.

This can easily be fixed by using fuels with higher octane grades. As recommended by Audi in their owner manuals, premium gasoline is something every car owner is encouraged to use. Fuel with octane grades equal to or above 91 is a good fit to fix engine knocking.

However, if you hear loud engine knocking, it´s best to stop the car immediately and call your dealer. Most likely, your car needs to be drained of its fuel, and the fuel filter will need to be replaced.

Finally, it´s good to know that slight engine knocking is a normal occurrence, especially if you´re towing with the car or temporarily using gasoline with an octane rating between 87 – 91 (which is lower than recommended but still safe in most cases).

Does The Audi A6 Have Good Gas Mileage?

As can be expected, the Audi A6 is a large sedan with some powerful engines which means the fuel economy isn’t the best. However, overall it’s not that bad either.

2019 – present

Engine	Combined MPG	City MPG	Highway MPG
3.0-liter 6-cylinder	24	21	30
2.0-liter Inline Four	28	25	34

2011 – 2018

Engine	Combined MPG	City MPG	Highway MPG
3.2-liter 6-cylinder	24	21	30
3.0-liter 6-cylinder	22	19	28
2.0-liter 4-cylinder	28	25	33
3.0-liter 6-cylinder Diesel	30	25	38

2004 – 2011

Engine	Combined MPG	City MPG	Highway MPG
4.2-liter 8-cylinder	18	16	23
3.2-liter 6-cylinder	22	18	28
3.1-liter 6-cylinder	21	18	27
3.0-liter 6-cylinder	21	18	26
2.7-liter 6-cylinder	19	16	23

1997 – 2004

Engine	Combined MPG	City MPG	Highway MPG
4.2-liter 8-cylinder	18	15	23
3.0-liter 6-cylinder	21	18	25
2.8-liter 6-cylinder	19	17	22
2.7-liter 6-cylinder	19	16	23

1994 – 1997

Engine	Combined MPG	City MPG	Highway MPG
2.8-liter 6-cylinder	19	16	23

What’s The Gas Tank Size Of An Audi A6?

To keep the car more on the road and less at a gas station, the fuel tank capacity is the one factor that counts the most. The current generation Audi A6 has a 19.3 gallons fuel tank, which decreased from 19.8 gallons for the 4th generation. The diesel variant on the 4th generation had a 19.3 gallons tank.

The third generation of the Audi A6 had a 21.1 gallons fuel tank, just like the 1st generation. The second-generation Audi A6 had a smaller 18.5 gallons fuel tank.

Generation	Gas Tank
5th Generation	19.3 Gal
4th Generation Gasoline	19.8 Gal
4th Generation Diesel	19.3 Gal
3rd Generation	21.1 Gal
2nd Generation	18.5 Gal
1st Generation	21.1 Gal

Sources

• Audi A6 Owners Manual 2022
• Audi A6 Owners Manual 2020
• Audi A6 Owners Manual 2016
• Audi A6 Owners Manual 2014
• Audi A6 Owners Manual 2010
• Fuel Economy Audi A6
• Audi A6 Wikipedia