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Types Of Gas A Cadillac XT6 Takes (Explained)

Types Of Gas A Cadillac XT6 Takes (Explained)

Today we will dive into various fuel-related characteristics of the Cadillac XT6, such as what gas it takes, types of fuels that can or should not be used, its mileage, and the size of the gas tank. Let’s start with a quick answer:

Cadillac XT6, with a 3.6L engine, take regular unleaded gasoline with an octane rating of 87. XT6, with a 2.0L engine, take premium gasoline with an octane rating of 91.

However, this doesn’t tell us the whole story. In the article below, we’ll discuss what kind of gasoline is used for what engine. Furthermore, we’ll discuss different additives that can and can’t be used, what percentage of ethanol is acceptable, and the gas tank size of the different XT6 generations. Read on!

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Infographic explaining the different fuel types for a Cadillac XT6.

Does The Cadillac XT6 Require Premium Gas?

The following table gives a quick overview of the different types of engines used in XT6, the year these were used, and the recommended fuel for each engine type.  

Engine (Year)Fuel Requirement 
3.6 L 6 Cylinder (2020-22)Regular gasoline (Octane rating 87)
2.0 L 4 Cylinder (2021-22)Premium unleaded gasoline (octane rating 91)
87 octane, 89 octane and 91 octane fuel levels explained

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

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

A wide range of petroleum products is now available in the market. It’s not always clear to the consumer what products are good and which aren’t because it is difficult to identify which products are safe and beneficial. Therefore in this section, we take a close look at the popular products and, based on Cadillac’s recommendation, determine if it is safe to use.

Reformulated Gasoline

Fossil fuels are the predominant fuel used throughout the world. Fossil fuels are also a significant contributor to the greenhouse effect and global warming due to toxic byproducts produced because of their burning. The RFG (Reformulated Gasoline) program was launched to counter the high level of smog in various cities in the US.

RFG is a cleaner-burning fuel and produces much lower toxins, such as sulfur and carbon monoxide, which are responsible for producing smog. Congress launched the RFG program in 1990, and since then, many cities across the nation have adopted it, and as a result, the smog levels have reduced considerably.

As per the Cadillac owner’s manual, the general recommendation is that fuel should be sulfur-free or low in sulfur content and have an octane rating, depending upon the engine, between 87 and 91. Reformulated gasoline meets these criteria and is, therefore, completely safe to use.

Gasoline/Oxygenated Blends Or E-85

More and more states are implementing laws that require the use of fuels that are relatively less harmful to the environment and public health. As a result, a very high percentage of gas sold in the USA is oxygenated with 10% ethanol, called E10.

The general recommendation regarding ethanol-blended fuel is that Cadillac prohibits using any fuel labeled greater than 15% ethanol by volume for its gas engines. Hence, mid-level ethanol blends (16–50% ethanol) are not allowed, but E10 and E15 are safe to use.

Ethanol levels for cars explained, E10, E15 and E85

The most popular of the oxygenated blended fuels is called FlexFuel. It contains 85% ethanol by volume. Car manufacturers have developed specialized engines that run on FlexFuel and conventional fuel. Cadillac prohibits using E85 with the XT6 because its use can harm the engine and the fuel supply system.

Furthermore, they also do not allow gas that has methanol as an oxygenating agent.

Gasoline With Added Materials

Typically, car manufacturers recommend against the use of fuel additives. Fuel additives are usually sold as octane-boosting substances or advertised to help keep your engine clean.

Boosting octane is a reasonably useless practice since it’s recommended and safer for your engine to buy premium gasoline at a certified retailer. Furthermore, cleaning additives are also advised against because they typically contain silicones or metallic, damaging the engine instead of cleaning it.

Therefore, Cadillac instead recommends using TOP TIER gasoline sold by certified retailers. This type of gasoline already has all the proper additives mixed into it, and it has been scientifically proven that this gasoline helps keep your engine clean and perform optimally. It also doesn’t cost any more than non-TOP TIER gasoline. You can find a retailer on

If for whatever reason, you don’t have access to TOP TIER gasoline sold by certified retailers, Cadillac advises you to use their own certified additive. Cadillac sells this additive as ‘ACDelco Fuel System Treatment Plus’. Cadillac advises you to add this to your fuel tank at every oil change (every 9,000 miles). The reason for using this is that this will keep your engine deposit free and, therefore, in optimum condition.

Gasoline With MMT

MMT or Methylcyclopentadienyl manganese tricarbonyl is added to enhance the fuel’s octane rating. Although it enhances the octane content, resulting in better efficiency, the long-term damage it causes to public health and the vehicle’s health outweigh its benefits. 

Studies have shown that MMT has a higher level of hydrocarbon emission. As a result, public health agencies put up a strong front against its use. Moreover, it has been shown to cause increased spark plug deposits and plugging of monolithic converters.

Cadillac prohibits using fuel that contains metals, such as methylcyclopentadienyl manganese tricarbonyl (MMT), which has been found to damage the emissions control system and spark plugs.

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

Hearing a slight knocking sound coming from the engine is normal. Especially when the car is performing at peak levels, such as when towing, a slight knocking sound can be heard. However, if this knocking sound becomes very audible and happens right after refilling, you may have more significant problems.

First off, in this case, it’s very likely you’re using gasoline with a lower-than-recommended octane rating. For example, Cadillac states 87 octane can be used in some instances even though 91 or 93 octane is recommended. However, if this creates a situation where you hear a loud knocking from the engine, it’s advised to stop immediately.

This knocking noise tells you the engine is misfiring because it can’t handle the octane level used. It’s best to stop your car immediately and call your dealer or garage. Your car will need to be drained from its fuel, and the fuel filter will need to be replaced. Continuing to drive will result in severe engine damage.

Does The Cadillac XT6 Have Good Gas Mileage?

The Cadillac XT6 uses 2.0L and 3.6L engines in its first generation. The 3.6L AWD is slightly less efficient in mileage per gallon than the FWD version. Similarly, the 2.0L FWD is somewhat more fuel-efficient than the AWD variant. 

black cadillac xt6 parked in parking lot
Engine/TypeHighway (MPG)City (MPG)Combined MPG
2.0  L AWD Premium gas232126
2.0 L FWD Premium gas232127
3.0 L (AWD) Regular gas211825
3.0 L (FWD) Regular gas211926

What’s The Gas Tank Size Of the Cadillac XT6?

The following table shows the tank size of the Cadillac XT6. The AWD versions in both the 2.0L and 3.6L have slightly larger tanks. The current size for the AWD is 19.0 gallons in both the 2.0L and 3.6L versions, while it is 22 gallons for the FWD.

Engine/YearGas Tank (gallons)
3.6 L FWD 2020-2219.0
3.6 L AWD 2020-2222.0
2.0 L FWD 2021-2219.0
2.0 L AWD 2021-2222.0


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