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Types Of Gas A GMC Sierra Uses (All Generations)

In this age of information, misinformation is getting more and more common. Our team here at “thedriveradviser” is putting in a lot of effort to give you accurate – either research-based or official – answers. Our team carries out strenuous research and then presents the data to ensure that you get the correct answers. On this blog, we will answer all the fuel-related questions. The main one would be what gas you should be adding to your GMC Sierra.

Across all generations, we have engines that require regular unleaded gasoline with 87 of octane, and those which 91 or higher are recommended. Apart from the regular gasoline engines, GMC Sierra has engines capable of running E85 as well. All trim levels are capable of running on 87 except for the 6.2L variant that has 93 recommended.

This doesn’t tell us the whole story. To make it clear, we have discussed everything in detail. We have divided this blog into a couple of sections. We’ll look at what kind of gas is needed for all generations of the Sierra and the available engine types. We’ll also look at if additives are needed, fuel mileage, and tank size. Read on!

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Fuel Requirements Based On Engine Type

There are four generations in total, each having a wide range of trim levels with many engine options – which we will cover in this article.

First Generation 1999-2006

According to the owner’s manual, you don’t have to change to a higher octane. If you hear a slight pinging/knocking sound when accelerating or going uphill, it’s nothing to worry about. When the sound is very loud, then it would mean your engine needs service.

But to be safe, it’s better to go for the mid-grade or premium for those above 6L engines. As in the later generations, the bigger displacement engines had specified higher octane for 6.2-liter engines.

EngineFuel Requirement
4.3L V6Regular 87 Octane (pump gas)
4.8L V8Regular 87 Octane (pump gas)
5.3L V8Regular 87 Octane (pump gas)
6.0L V8Regular 87 Octane (pump gas)
6.6L V8Regular 87 Octane (pump gas)
8.1L V8Regular 87 Octane (pump gas)

Also read: How Many Miles Can A GMC Sierra 1500 Last? (Answered)

Second Generation 2007-2013

The second generation has engines that can support flex-fuel. Look for the 8th digit of the VIN Code, the 5.3L V8 with VIN code 0, 5.3L V8 with VIN code 3, 6L V8 with VIN code J, and 6.2L with VIN code 2. All are flex-fuel appropriate and can run on flex-fuel without a problem. You can also look at the gas cap. The color should be yellow.

EngineFuel Requirement
4.3L V687 rated can be used but preferably 91 or higher
4.8L V887 rated can be used but preferably 91 or higher
5.3L V8Mid-Grade 91 or higher octane rated gasoline, Flex Fuel*
6.0L V8Mid-Grade 91 or higher octane rated gasoline, Flex Fuel*
6.2L V8Mid-Grade 91 or higher octane rated gasoline, Flex Fuel*

Third Generation 2015-2018

EngineFuel Requirement
4.3L V687 rated can be used but preferably 91 or higher
5.3L V887 rated can be used, but preferably Mid-Grade 91 or higher octane rated gasoline
6.0L V8Mid-Grade 91 or higher octane rated gasoline
6.2L V8Premium with 93 rated octane

Fourth Generation 2019-Present

EngineFuel Requirement
2.7L inline-4Regular 87 Octane (pump gas) or higher
4.3L V6Regular 87 Octane (pump gas) or higher
5.3L V8Regular 87 Octane (pump gas) or higher
6.2L V8Premium with 93 rated octane

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

GMC Recommendation

TOP TIER Detergent Gasoline is the recommended additive. 87 or higher octane-rated gasoline is required in GMC Sierra except for the 6.2 Liter in which it’s recommended to have the premium 93 octane-rated. There are plenty of other additives floating in the market, but not all of them are good for your engine. Later in this blog, we will cover those additives as well.

If you are following all the guidelines given by the manufacturer, your GMC will last you thousands of miles. To know how you can get better miles, you can refer to this blog, where you will find all the common problems that can occur in a GMC Sierra and how it performs against competitors. How many miles a GMC Sierra can last

Reformulated Gasoline

Introduced not so long ago is the reformulated gasoline known as RFG. This type of gas burns more cleanly and emits fewer pollutants and less smog into the atmosphere. Therefore, RFG is helpful in areas that have poor air quality index. It is also beneficial in the regions that have strict emission standards.

RFG will not harm your engine in any way. It is safe to use, and it is also said to have increased the mpg numbers on top of producing fewer toxins.

Gasoline/Oxygenated Blends Or E-85

There are many oxygenated blends available in the market. Vehicles produced before 2011 would run fine on ethanol percentages up to 10% by volume. In 2011, the EPA allowed up to 15% ethanol by volume mixed with 85% regular gasoline.

More than 15% ethanol would harm the engine. The warranty does not cover those damages that are done to the engine by adding improper additives. The E85, also known as the flex-fuel, should only be added in vehicles specifically designed to run on flex-fuel. To know for sure whether or not the car in question is flex-fuel appropriate or not, follow the steps below:

  • Look at the gas cap, you will find E85 imprinted on it if it’s made to run flex fuel.
  • If the cap gas, it might be on the back of the gas door.
  • Usually, as a standard, flex-fuel vehicles have yellow gas caps.

When you have made sure that your vehicle is flex-fuel-appropriate, then you need to make sure you are following the necessary protocols.

  • Do not add less than 3 gallons when you are interchanging fuels.
  • Do not park your vehicle right after a refill, at least drive it for about 8 miles.

Do not add any additives when you are running on flex-fuel. It might do more damage than good. 

Gasoline With Added Materials

The market is filled with all kinds of additives, and most of them are harmful to your engine. GMC advises using only TOP TIER Detergent Gasoline to help clean your engine’s internals and help keep you up to the mark on emission standards.

You should not be using any other additive. Most of the octane boosters in the market have metals that are going to damage your engine. You are not allowed to mix methanol, MMT, more than 15% ethanol, etc. 

Gasoline With MMT

This additive, MMT, stands for Methylcyclopentadienyl Manganese Tricarbonyl that helps increase the octane rating of a poor-quality fuel. This additive is strongly advised against, and you should not be adding this to your gas tank. This additive is recommended against because it damages the emissions control system on top of reducing spark plugs’ life.

Biodiesel

This is an additive that can be added not more than 20% by volume along with diesel. It reduces carbon emissions, and it also helps give better mileage. There are no diesel variants for the GMC Sierra in which you can use this additive.

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

A very faint knocking sound from the engine is typical. However, if you have started to hear banging noises from the engine after refilling, then most probably, the quality of the fuel is the culprit here. If the engine’s octane requirements are not met, and the fuel has less than the minimum required octane, that results in knocking.

If you hear a very loud knocking sound, you should immediately take your GMC Sierra to the dealership and check it. To get rid of the knocking, you can fill the tank with mid-grade or premium gasoline. If you still hear knocking sound after running on mid-grade or premium fuel, then your engine needs service.

Does the GMC Sierra Have Good Gas Mileage?

GMC vehicles are not known for good gas mileage. Most of them have low mpg. The actual mpg always comes out lower than the GMC’s given numbers.

First Generation 1999-2006

EngineLowest Combined MPGHighest Combined MPG
4.3L V61520
4.8L V81316
5.3L V81418
6.0L V81013
6.6L V8810
8.1L V869

Second Generation 2007-2013

EngineLowest Combined MPGHighest Combined MPG
4.3L V61520
4.8L V81419
5.3L V81521
5.3L V8 Flex Fuel1116
6.0L V82023
6.0L Hybrid2023
6.2L V81318
6.2L V8 Flex-fuel913

Third Generation 2015-2018

EngineLowest Combined MPGHighest Combined MPG
4.3L V61823
4.3L Flex Fuel1216
5.3L V81519
6.0L V81317
6.2L V81115

Fourth Generation 2019-Present

EngineLowest Combined MPGHighest Combined MPG
2.7L inline-42023
4.3L V61519
5.3L V81418
5.3L V8 E851115
6.2L V81620

What’s The Gas Tank Size Of A GMC Sierra?

First Generation 1999-2006

TypeQuantity
Short Bed26 gallons
Long Bed34 gallons
Chassis Cab (pickup box delete)34 gallons
Chassis Cab 350027 gallons front (if equipped, 23 gallons rear)
Chassis Cab 3500 (California)24 gallons front (if equipped, 23 gallons rear)
Chassis Cab 350027 gallons
Chassis Cab 3500 (California)27 gallons
Chassis Cab23 gallons front (if equipped, 18 gallons rear)
Chassis Cab23 gallons

Second Generation 2007-2013

TypeQuantity
1500 Series Standard and Short Box26 gallons
1500 Long Box34 gallons
2500 Series Standard Box26 gallons
2500 Series and 3500 Series Long Box34 gallons
Chassis Cab 350050 gallons
Chassis Cab 3500 front tank27 gallons
Chassis Cab 3500 rear tank (if equipped)23 gallons

Third Generation 2015-2018

TypeQuantity
1500 Series Standard and Short Box26 gallons
1500 Long Box34 gallons
2500 Series and 3500 Series Standard Box36 gallons
2500 Series and 3500 Series Long Box36 gallons
Chassis Cab 350063.5 gallons
Chassis Cab 3500 front tank23.5 gallons
Chassis Cab 3500 rear tank (if equipped)40 gallons

Fourth Generation 2019-Present

TypeQuantity
Standard and Short Box (except 2WD Diesel)24 gallons
Long Box36 gallons

How Much Does It Cost To Fill Up A GMC Sierra

There are tons of different sizes of gas tanks available, so let’s take a 30-gallon gas tank as a point of reference. If you happen to be in California, you would be paying the highest price per gallon, which is $4.388, and for a full 30 gallons, your total would be approximately $130.

On the other hand, if you live in Texas or Mississippi, you would be paying the least amount per gallon, which is $2.816, and for 30 gallons, your total would be approximately $85.

Our research has shown that gas prices are going up steadily. With the range of gas tanks being wide, the price range becomes wide as a result. So overall the price for a full tank, from the smallest size available to the largest one, can be somewhere between $64-$280 from the cheapest to the most expensive. These prices have been calculated at the time of writing this article.

Sources