The quick answer: open the fuel door using the interior release or by pressing on the outside of the door, then refuel according to whether your model uses a capless filler or a traditional gas cap. If your Terrain is capless, there is no cap to remove.
In this article, we explain where to find the fuel-door release, how to tell if your model uses a capless filler or a traditional cap, and the step-by-step process to open, fuel, and close the gas tank on a 2018 GMC Terrain.
Ways to open the fuel door
Two common methods exist, depending on trim and market. Choose the method your vehicle supports to access the filler neck.
- Interior release method: On most trims, locate the fuel-door release switch or lever on the driver's door panel near the armrest or window controls. Press or pull the switch to pop the fuel door open.
- Exterior press method: If there is no convenient interior release, stand at the rear left side of the vehicle and firmly press on the outside of the fuel door until it pops outward and hinges open.
After using one of these methods, the filler neck should be exposed and ready for fueling. If the door doesn’t release, ensure the vehicle is unlocked and try again; some trims require the ignition to be off or doors unlocked for the release to work.
Capless filler vs traditional gas cap
Knowing which type your 2018 Terrain uses will determine how you fuel it.
- Capless filler: Many 2018 Terrain models use a capless fueling system. There is no separate gas cap to remove. With the fuel door open, insert the nozzle directly into the filler neck and fuel as normal.
- Traditional gas cap: If your Terrain has a gas cap behind the door, remove the cap by turning it counterclockwise, fuel, then replace the cap and twist until it clicks to seal.
Once fueling is complete, close the fuel door securely. If you removed a cap, ensure it’s tightened and that the door is fully closed.
Fueling steps and aftercare
Follow these practical steps to complete the fueling process cleanly and safely.
- Insert the nozzle and fill until the pump shuts off automatically. Avoid topping off after the automatic shutoff.
- If your vehicle uses a cap, reattach it and ensure the seal is snug and the cap clicks into place.
- Close the fuel door firmly so it sits flush against the body of the vehicle.
With the door closed and the vehicle secure, you’re ready to drive away. Keep your receipt if you need it for records or budgeting.
Summary
Opening the gas tank on a 2018 GMC Terrain is straightforward: release the fuel door from inside or pop it from outside, then fuel according to whether you have a capless filler or a traditional gas cap, and finally close everything securely. Always ensure the door is fully closed and the cap (if present) is properly tightened after fueling.