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!
Want to save money on gasoline? earn up to $0.25/gallon every time you fill up? GetUpside is a free-to-use cashback app for US gas stations. Use coupon code “THEDRIVERADVISER25” and earn an additional $0.25/gallon the first time! Click here to download the app for Android or iOS.
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.
Engine | Fuel Requirement |
4.3L V6 | Regular 87 Octane (pump gas) |
4.8L V8 | Regular 87 Octane (pump gas) |
5.3L V8 | Regular 87 Octane (pump gas) |
6.0L V8 | Regular 87 Octane (pump gas) |
6.6L V8 | Regular 87 Octane (pump gas) |
8.1L V8 | Regular 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.
Engine | Fuel Requirement |
4.3L V6 | 87 rated can be used but preferably 91 or higher |
4.8L V8 | 87 rated can be used but preferably 91 or higher |
5.3L V8 | Mid-Grade 91 or higher octane rated gasoline, Flex Fuel* |
6.0L V8 | Mid-Grade 91 or higher octane rated gasoline, Flex Fuel* |
6.2L V8 | Mid-Grade 91 or higher octane rated gasoline, Flex Fuel* |
Third Generation 2015-2018
Engine | Fuel Requirement |
4.3L V6 | 87 rated can be used but preferably 91 or higher |
5.3L V8 | 87 rated can be used, but preferably Mid-Grade 91 or higher octane rated gasoline |
6.0L V8 | Mid-Grade 91 or higher octane rated gasoline |
6.2L V8 | Premium with 93 rated octane |
Fourth Generation 2019-Present
Engine | Fuel Requirement |
2.7L inline-4 | Regular 87 Octane (pump gas) or higher |
4.3L V6 | Regular 87 Octane (pump gas) or higher |
5.3L V8 | Regular 87 Octane (pump gas) or higher |
6.2L V8 | Premium with 93 rated octane |
Diesel Options for the GMC Sierra
There are also several years where diesel was available via the Duramax engine. Not only will some drivers prefer a diesel engine for the fuel efficiency, but the Allison 1000 Transmission that’s found in most of these models is generally considered more reliable.
- 2001-2004: 6.6L Duramax LB7 V8
- 2004-2006: 6.6L Duramax LLY V8
- 2006-2007: 6.6L Duramax LBZ V8
- 2007-2010: 6.6L Duramax LMM V8
- 2011-2016: 6.6L Duramax LML V8
- 2017-2019: 6.6L Duramax L5P V8
- 2020-Present: 3.0L Duramax I6 (1500 model), 6.6L Duramax L5P V8 (HD models)
Please note, these are the main diesel engine options for each specified year range, and each was available in various GMC Sierra models including 1500HD, 2500HD, and 3500HD series.
The 3.0L Duramax I6 introduced in 2020 was the first time a diesel engine was offered in the light-duty 1500 model. The 6.6L Duramax V8 continues to be available in the Sierra HD models.
What Types Of Gasoline Can And Can’t Be Used?
GMC Recommendation
TOP TIER Detergent Gasoline is the recommended additive for many GMC models like the GMC Terrain and Canyon, among others. 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 post, we will cover those additives as well but with the right care you can expect a GMC Sierra 1500 to last well over 150,000 miles or much more.
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.
Just like with other GMC models, 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 and it’s a good idea to check out real world tests like the one below before getting to excited:
First Generation 1999-2006
Engine | Lowest Combined MPG | Highest Combined MPG |
4.3L V6 | 15 | 20 |
4.8L V8 | 13 | 16 |
5.3L V8 | 14 | 18 |
6.0L V8 | 10 | 13 |
6.6L V8 | 8 | 10 |
8.1L V8 | 6 | 9 |
Second Generation 2007-2013
Engine | Lowest Combined MPG | Highest Combined MPG |
4.3L V6 | 15 | 20 |
4.8L V8 | 14 | 19 |
5.3L V8 | 15 | 21 |
5.3L V8 Flex Fuel | 11 | 16 |
6.0L V8 | 20 | 23 |
6.0L Hybrid | 20 | 23 |
6.2L V8 | 13 | 18 |
6.2L V8 Flex-fuel | 9 | 13 |
Third Generation 2015-2018
Engine | Lowest Combined MPG | Highest Combined MPG |
4.3L V6 | 18 | 23 |
4.3L Flex Fuel | 12 | 16 |
5.3L V8 | 15 | 19 |
6.0L V8 | 13 | 17 |
6.2L V8 | 11 | 15 |
Fourth Generation 2019-Present
Engine | Lowest Combined MPG | Highest Combined MPG |
2.7L inline-4 | 20 | 23 |
4.3L V6 | 15 | 19 |
5.3L V8 | 14 | 18 |
5.3L V8 E85 | 11 | 15 |
6.2L V8 | 16 | 20 |
What’s The Gas Tank Size Of A GMC Sierra?
First Generation 1999-2006
Type | Quantity |
Short Bed | 26 gallons |
Long Bed | 34 gallons |
Chassis Cab (pickup box delete) | 34 gallons |
Chassis Cab 3500 | 27 gallons front (if equipped, 23 gallons rear) |
Chassis Cab 3500 (California) | 24 gallons front (if equipped, 23 gallons rear) |
Chassis Cab 3500 | 27 gallons |
Chassis Cab 3500 (California) | 27 gallons |
Chassis Cab | 23 gallons front (if equipped, 18 gallons rear) |
Chassis Cab | 23 gallons |
Second Generation 2007-2013
Type | Quantity |
1500 Series Standard and Short Box | 26 gallons |
1500 Long Box | 34 gallons |
2500 Series Standard Box | 26 gallons |
2500 Series and 3500 Series Long Box | 34 gallons |
Chassis Cab 3500 | 50 gallons |
Chassis Cab 3500 front tank | 27 gallons |
Chassis Cab 3500 rear tank (if equipped) | 23 gallons |
Third Generation 2015-2018
Type | Quantity |
1500 Series Standard and Short Box | 26 gallons |
1500 Long Box | 34 gallons |
2500 Series and 3500 Series Standard Box | 36 gallons |
2500 Series and 3500 Series Long Box | 36 gallons |
Chassis Cab 3500 | 63.5 gallons |
Chassis Cab 3500 front tank | 23.5 gallons |
Chassis Cab 3500 rear tank (if equipped) | 40 gallons |
Fourth Generation 2019-Present
Type | Quantity |
Standard and Short Box (except 2WD Diesel) | 24 gallons |
Long Box | 36 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.
Overall, the Sierra 1500 is a great truck without a lot of issues, especially in the middle generations. So while it’s not the cheapest in terms of gas, it’s a solid pick even on the used market.
Sources
- https://www.caranddriver.com/gmc/sierra-1500/specs
- https://www.autoevolution.com/gmc/sierra/
- https://www.autolist.com/gmc-sierra+1500/gmc-sierra+1500-generations
- https://ownersman.com/manuals/2001-GMC-Sierra-owners-manual
- https://my.gmc.com/content/dam/gmownercenter/gmna/dynamic/manuals/2010/gmc/sierra_1500/2010_gmc_sierra_owners.pdf
- https://my.gmc.com/content/dam/gmownercenter/gmna/dynamic/manuals/2016/GMC/Sierra/2k16sierra2ndPrint.pdf
- https://fueleconomy.gov/feg/bymodel/2001_GMC_Sierra.shtml
- https://www.fueleconomy.gov/feg/bymodel/2012_gmc_sierra.shtml
- https://www.fueleconomy.gov/feg/bymodel/2016_GMC_Sierra.shtml
- https://www.fueleconomy.gov/feg/bymodel/2021_GMC_Sierra.shtml
Hi! My name is Stefan; I’m the owner and lead writer at TheDriverAdviser.com.
I’m an active writer on this blog myself, as well as a novice car mechanic. For the really technical stuff, I find writers with experience as a mechanic or who have studied mechanical engineering.
Read more about our fantastic team on our about page!