Tank figures are the manufacturer's rated capacity, sorted smallest tank first. The EPA doesn't rate fuel economy for heavy-duty pickups and vans (over 8,500 lb gross vehicle weight), so these trims have no official MPG or range.
What it costs to fill up a 2018 GMC Sierra 3500HD
$153.72to fill the 36.0-gallon tank from empty with regular, at this week's US average of $4.27 a gallon.
At 36.0 gallons, the Sierra 3500HD's largest tank ranks second of the five 2018 pickups compared here. The Ford F-350 Super Duty carries the most (48.0 gal) and the Nissan Titan XD the least (26.0 gal).
Other 2018 pickups of a similar size, one model per brand.
2018 GMC Sierra 3500HD fuel system recalls
NHTSA lists 2 fuel-system recalls for the 2018 GMC Sierra 3500HD, out of 6 recalls in total. A recall applies only to the vehicles named in it, so check your VIN.
Storage · Tank assemblyFeb 2, 2023 · NHTSA 23V047000 · General Motors, LLC · 22,132 vehicles
General Motors, LLC (GM) is recalling certain 2017-2019 Chevrolet Silverado 2500, 3500, and GMC Sierra 2500, 3500 vehicles equipped with a dual fuel tank option. The rear fuel tank may collapse and prevent the fuel pump from transferring fuel to the front tank, resulting in an engine stall.
Risk and remedy
Risk: An engine stall increases the risk of a crash.
Remedy: Dealers will inspect the fuel tank and fuel pump module, replacing them as necessary. Dealers will also add a vent hose to the rear tank assembly. Repairs will be performed free of charge. An interim owner notification letter informing owners of the safety risk was mailed on March 15, 2023. Owner notification letters were mailed June 21, 2023. Owners may contact Chevrolet customer service at 1-800-222-1020 or GMC customer service at 1-800-462-8782. GM's number for this recall is N222368030.
Storage · Tank assemblyFeb 7, 2019 · NHTSA 19V088000 · General Motors Llc · 18,574 vehicles
General Motors, LLC (GM) is recalling certain 2016-2018 GMC Sierra 3500 and Chevrolet Silverado 3500 trucks equipped with gasoline engines and dual fuel tanks. The fuel-level sensor in the front tank may stick in a low-level position, allowing the rear tank to overfill the front tank.
Risk and remedy
Risk: If the front tank overfills, the excess pressure may cause the front tank to expand and contact the driveshaft, possibly resulting in a hole in the tank. The hole will leak fuel, which in the presence of an ignition source, can increase the risk of a fire.
Remedy: GM has notified owners, and dealers will replace the rear-tank fuel-pump module, inspect the front tank and, if necessary, replace the front tank, free of charge. The recall began July 30, 2019. GM's number for this recall is N182204190.
What is the fuel tank capacity of the 2018 GMC Sierra 3500HD?
The 2018 GMC Sierra 3500HD holds 36.0 gallons (136 liters) on every trim we list.
How many gallons and liters does the 2018 GMC Sierra 3500HD gas tank hold?
The 2018 GMC Sierra 3500HD tank holds 136 liters, or 36.0 gallons in US gallons.
Does 4WD change the 2018 GMC Sierra 3500HD gas tank?
No. 4WD and RWD versions of the 2018 GMC Sierra 3500HD use the same 36.0 gal tank.
What gas does the 2018 GMC Sierra 3500HD take?
Flex-fuel (unleaded/E85). The label inside the fuel door confirms it for your car.
How much does it cost to fill up a 2018 GMC Sierra 3500HD?
At the US average of $4.27 a gallon for regular (EIA, week of October 26, 2026), filling the 36.0-gallon tank from empty costs $153.72. It ranges from $133.20 in the Gulf Coast to $212.04 in California.
How much does a full tank of gas weigh in a 2018 GMC Sierra 3500HD?
About 223 pounds for the 36.0-gallon tank. Gasoline weighs roughly 6.2 pounds a gallon.
Does the 2018 GMC Sierra 3500HD have a bigger gas tank than the Chevrolet Silverado 3500HD?
No, they match: both top out at 36.0 gallons in 2018.
Has the 2018 GMC Sierra 3500HD had a fuel pump or fuel system recall?
Yes. NHTSA lists 2 fuel-system recalls for the 2018 GMC Sierra 3500HD: 23V047000 (storage · tank assembly); 19V088000 (storage · tank assembly). Check your VIN at nhtsa.gov/recalls to see if your car is affected.
Sources
Tank sizes: manufacturer-rated capacities from US-market specifications, checked against independent references. Updated October 2026.
MPG and range: EPA ratings. Range is tank size times EPA MPG.
Fuel prices: U.S. Energy Information Administration, week of October 26, 2026 (this week's prices).