Ram 2500 fuel tank size

The Fluid Capacities charts list approximate fuel capacities by engine, cab and bed. The same figures apply to 2500 and 3500 models:

From the 2026 Ram 2500/3500 Owner's Manual (Fluid Capacities, pages 353 and 354), read October 29, 2026. Other model years can differ; check your own manual.

What fuel a Ram 2500 takes, by engine

From the 2026 Ram 2500/3500 Owner's Manual (Fuel Requirement: Gasoline Engine, page 345; Fuel Requirement: Diesel Engine, pages 347 and 348; Fuel Selection, pages 349 and 351), read October 29, 2026.

For the diesel, the manual says that below 20°F, or for long periods in colder-than-normal conditions, you should use Climatized Number 2 Diesel Fuel or dilute Number 2 diesel with 50% Number 1 Diesel Fuel to help prevent gelling. Do not use alcohol or gasoline as a fuel blending agent. If you accidentally fill a diesel truck with gasoline, do not start it; the manual says to call an authorized dealer for service.

Gasoline quality for the 6.4L

The 2026 manual says not to use E-85, gasoline containing methanol, or gasoline containing more than 15% ethanol (E-15), and to watch pump labels, which should clearly say if a fuel contains more than 15% ethanol. Using those blends may cause starting and drivability problems, damage critical fuel system components, cause emissions to exceed the applicable standard and/or turn on the Malfunction Indicator Light.

It recommends gasolines with detergents, corrosion and stability additives, TOP TIER Detergent Gasoline when available, and reformulated gasoline. It does not recommend fuel additives sold as octane enhancers, recommends gasoline without MMT, and says indiscriminate use of fuel system cleaning agents should be avoided. If you notice hard starting, stalling or hesitation, it suggests trying another brand of gasoline before considering service.

From the 2026 Ram 2500/3500 Owner's Manual (Fuel Requirement: Gasoline Engine; Reformulated Gasoline; Materials Added To Fuel; Gasoline/Oxygenate Blends; MMT In Gasoline; Fuel System Cautions, pages 345 and 346), read October 29, 2026.

How to refuel a Ram 2500

6.4L gas trucks. The fuel filler cap is behind the fuel filler door on the left side of the truck. Open the fuel door and remove the cap by turning it counterclockwise, laying the cap tether in the hook on the fuel filler door. Fully insert the nozzle, fill the truck, and when the nozzle clicks or shuts off, the tank is full. Remove the nozzle, reinstall the cap and close the door. Tighten the cap until you hear a click; the Malfunction Indicator Light may turn on if it is not secured properly. If the system finds a loose, improperly installed or damaged cap, a loose gas cap message appears in the instrument cluster: tighten the cap properly and push the right button to turn off the message.

6.7L diesel trucks. There is no fuel filler cap: a flapper door inside the filler pipe seals the system. The manual's steps:

• Open the fuel filler door.
• Insert the fuel nozzle fully into the filler pipe; the nozzle opens and holds the flapper door while refueling.
• Fill the vehicle with fuel. When the nozzle clicks or shuts off, the tank is full.
• Remove the fuel nozzle and close the fuel door.

The manual's Fill Locations illustration shows the Diesel Exhaust Fluid (DEF) fill location next to the diesel fuel fill location. If a diesel truck runs out of fuel, the manual says that once it is refueled, place the ignition in the ON position for 30 seconds, then turn it OFF and wait 30 seconds, and repeat this three times before cranking the engine. The manual also warns never to add fuel with the engine running, not to top off the tank after filling, and to always place portable fuel containers on the ground while filling them.

From the 2026 Ram 2500/3500 Owner's Manual (Refueling The Vehicle: Gasoline Engine; Loose Fuel Filler Cap Message; Refueling The Vehicle: Diesel Engine, pages 193 to 195), read October 29, 2026.

When the low fuel light comes on

Per the 2026 manual, the Low Fuel Warning Light turns on when the fuel level reaches approximately 3.2 gallons (12 L) and stays on until fuel is added. A single warning chime sounds with the low fuel warning.

From the 2026 Ram 2500/3500 Owner's Manual (Low Fuel Warning Light, page 139), read October 29, 2026.

Ram 2500 service at Elgin CDJR

Our Mopar service department services the Ram 1500, 2500 and 3500, including the Cummins 6.7-liter turbo diesel, diesel exhaust fluid (DEF) and emissions systems, and trailer-brake setups, along with routine maintenance, Express Lane oil changes, brakes, tires, recalls and warranty repairs. If your truck runs poorly after a fill-up or shows a check engine light, schedule a visit. If the Water in Fuel light stays on, or a diesel truck was filled with gasoline, do not start the engine; contact us first.

Our service department is open Monday to Friday 7 a.m. to 7 p.m. and Saturday 7:30 a.m. to 4 p.m. Elgin CDJR is at 1500 W. Lake St. in Streamwood. Get directions.

Schedule service online, or see our Ram service center page.