2026 Ram 2500 and 3500 Diesel Maintenance Guide

2026 Ram Heavy Duty Maintenance Schedule
6.7L Cummins Turbo Diesel
Schedule Service
Service Interval Maintenance Due
Every 7,500 miles
  • Check the Diesel Exhaust Fluid level and refill when necessary.
  • Rotate the tires.
  • Inspect the front end and lubricate serviceable fittings when equipped.
  • Inspect the CV and universal joints.
Every 12,000 miles Replace the cabin air filter.
Every 15,000 miles
  • Change the engine oil and oil filter, or sooner when prompted by the oil life system.
  • Replace both engine-mounted fuel filters.
  • Inspect the engine air cleaner filter and replace it when necessary.
  • Inspect the front suspension, tie rod ends and boot seals for leaks, wear, looseness or damage.
Every 22,500 miles
  • Inspect the brake linings and parking brake operation.
  • Inspect the drive belt and replace it when necessary.
  • Inspect the front and rear axle surfaces for leaks. Check the fluid level when leakage is suspected.
Every 30,000 miles
  • Inspect the wheel bearings.
  • Inspect the transfer case fluid on four-wheel-drive trucks.
Every 60,000 miles
  • Change the automatic transmission fluid.
  • Change the transfer case fluid on four-wheel-drive trucks.
Every 75,000 miles Replace the crankcase ventilation filter.
At 97,500 miles Flush and replace the power steering fluid.
At 150,000 miles or 10 years Flush and replace the engine coolant, whichever interval comes first.

Engine oil limit: Never exceed 15,000 miles, 12 months or 500 engine hours between oil changes. Follow the oil life system when it requests service sooner.

Frequent towing, fleet operation, off-road driving and other severe use may require earlier axle or transfer case fluid service.

Severe-Duty Maintenance for a Ram 2500 or 3500 Diesel

The maintenance chart above shows the standard schedule, but plenty of Ram Heavy Duty trucks live a harder life than the average vehicle. Ram identifies high temperatures, repeated short trips, heavy loading, trailer towing, off-road driving and law enforcement use as severe service conditions.

Ram does not publish a separate fixed oil-change mileage for severe use. Instead, the truck's duty-cycle-based oil life system can call for service before the normal 15,000-mile maximum. Follow the Oil Change Due message when it appears, even when the truck has fewer miles than expected.

Maintenance That Changes With Heavy Use
Maintenance Item Severe-Duty Guidance
Engine oil and filter Severe service may shorten the oil-change interval. Change the oil when prompted and never exceed 15,000 miles, 12 months or 500 engine hours, whichever comes first.
Front and rear axle fluid Change the axle fluid when the truck is used for police, taxi, fleet, off-road or frequent trailer-towing operation.
Transfer case fluid On 4x4 trucks, change the transfer case fluid at the scheduled inspection interval when the truck is used for police, taxi, fleet or frequent trailer-towing operation.
Engine air cleaner filter Inspect the filter at every oil change when the truck is driven in dusty or off-road conditions. Replace it when needed.

What Counts as Severe Use?

  • Frequent trailer towing
  • Regular operation with heavy payloads
  • Repeated short trips
  • Driving in high ambient temperatures
  • Off-road or unusually dusty operation
  • Police, taxi or fleet operation

Off-road use also requires the engine oil level to be kept at the full mark on the dipstick. Ram recommends checking the oil level every 3,000 miles after the fully warmed engine has been shut off for at least 30 minutes and the truck is parked on level ground.

The important part is the truck's actual workload. A lightly used diesel and a 3500 towing every week may show the same mileage while putting very different demands on their oil, axles and transfer case.

6.7L Cummins Engine Oil and Filter Changes

Ram sets the maximum engine oil and filter interval for the 2026 6.7L Cummins diesel at 15,000 miles, 12 months or 500 engine hours, whichever comes first. The truck's oil change indicator may call for service sooner based on its duty cycle and how it has been driven.

That oil life message matters more than simply counting miles. Frequent towing, long periods of idling and demanding work can use up the oil's service life faster than steady unloaded highway driving. When the instrument cluster displays Oil Change Due, the oil and filter are due for replacement.

2026 Ram 6.7L Cummins Engine Oil Requirements

Oil capacity with filter: 12 quarts

Above 0 degrees F: SAE 10W-30 engine oil meeting Ram Material Standard MS-10902 and API CK-4. Oil meeting Cummins CES 20081 may also be used.

Below 0 degrees F: SAE 5W-40 synthetic engine oil meeting Ram Material Standard MS-10902 and API CK-4.

Chicagoland temperatures can move across that 0 degree line quickly. Using the correct oil viscosity for the conditions helps protect the engine during cold starts while maintaining proper lubrication once the truck is working.

After an oil change, the oil change indicator must be reset so the truck can accurately track the next service interval. An authorized Ram dealer will reset the system after completing the service.

6.7L Cummins Fuel Filters and Water Separator

The 2026 Ram 2500 and Ram 3500 diesel use two engine-mounted fuel filters. Ram calls for both filters to be replaced every 15,000 miles.

Filter quality matters on a modern high-pressure diesel fuel system. The front-mounted filter must meet a 3-micron rating and the rear engine-mounted filter must meet a 5-micron rating. Ram warns that filters that fail to meet its filtration and water-separation requirements can shorten fuel-system life and reduce reliability.

What to do when the Water In Fuel light comes on

Stop the engine and drain the water from both fuel filters. If the warning light remains illuminated, leave the engine off until the water has been drained. Starting the engine with water still present in the filters can cause engine damage.

Diesel fuel can contain small amounts of water, which the separator collects before it reaches the fuel system. The truck monitors both filters and turns on the Water In Fuel indicator when draining is required.

A Water In Fuel light accompanied by a single chime may indicate a separator sensor or wiring problem instead of accumulated water. In that case, the truck should be inspected at our North Aurora Truck Repair Center.

Diesel Exhaust Fluid for the 6.7L Cummins

DEF and the diesel particulate filter handle different jobs in the emissions system. For a plain-English explanation, read our Ram diesel DPF vs. DEF maintenance guide. If your truck already has a warning on the dash, our guide to what to do when the Ram DEF system warning is on covers the next steps.

The 2026 Ram 2500 and Ram 3500 diesel use a Diesel Exhaust Fluid injection system and a Selective Catalytic Reduction catalyst to reduce nitrogen oxide emissions. The DEF gauge in the instrument cluster shows the amount of fluid remaining in the tank, and Ram calls for the level to be checked every 7,500 miles and refilled when necessary. There is a DEF gauge on the instrument cluster to display the DEF level in the tank.

Use Mopar DEF or an equivalent product that is API Certified to the ISO 22241 standard. Fluid that does not meet that standard may damage the system.

DEF refill basics

  • Stop filling at the first automatic shutoff.
  • Do not top off or overfill the DEF tank.
  • The gauge may take a few seconds, or several drives in very cold weather, to show the new level.
  • Clean spilled DEF with water and absorbent material.

DEF can freeze at or below 12 degrees F, but the truck has a heated DEF system and can continue operating while the fluid thaws. Overfilling leaves too little room for expansion and can damage the system when the fluid freezes.

If DEF is accidentally added to the diesel fuel tank, leave the engine off. Starting it can cause severe damage to the fuel pump, injectors and other fuel-system components.

Transmission, Transfer Case and Axle Maintenance

A Ram 2500 or Ram 3500 diesel is usually bought to work, tow or carry weight. That makes drivetrain fluid maintenance more important than it may be on a truck that spends its life hauling groceries and good intentions.

The regular maintenance schedule calls for automatic transmission fluid and 4x4 transfer case fluid changes at 60,000 and 120,000 miles. Transfer case fluid should also be inspected every 30,000 miles. Ram calls for earlier transfer case service when the truck is used for police, taxi or fleet operation, or frequent trailer towing.

Drivetrain Fluid Schedule
Service Regular Interval Heavy-Use Guidance
Automatic transmission fluid Change at 60,000 and 120,000 miles Watch for leaks, overheating or changes in shift quality
Transfer case fluid on 4x4 trucks Inspect every 30,000 miles. Change at 60,000 and 120,000 miles Change during the 30,000-mile service for fleet use or frequent trailer towing
Front and rear axle fluid Inspect axle surfaces for leakage every 22,500 miles Change the axle fluid for fleet, off-road or frequent trailer-towing use

Fluid type depends on the component and axle configuration. The eight-speed automatic transmission uses Mopar ATF 818 or an equivalent fluid that meets the same requirements. Four-wheel-drive trucks use Mopar BW44-44 Transfer Case Fluid.

Most front and rear axles use SAE 75W-85 HD Ram GL-5 synthetic lubricant. The 12.0-inch rear axle used on Ram 3500 dual-rear-wheel trucks requires SAE 75W-140 synthetic gear lubricant. Limited-slip axles also have specific additive requirements, so axle type needs to be confirmed before adding or replacing fluid.

Power Steering Fluid and Engine Coolant

Ram schedules a power steering fluid flush and replacement at 97,500 miles. The specified fluid is Mopar Power Steering Fluid +4 or Mopar ATF+4 Automatic Transmission Fluid.

Engine coolant is scheduled for replacement at 150,000 miles or 10 years. The 6.7L Cummins cooling system uses Mopar 10 Year/150,000 Mile OAT coolant and holds approximately 22 quarts. OAT coolant should never be mixed with HOAT or so-called globally compatible coolant. Mixing coolant types can reduce corrosion protection and require the system to be drained, flushed and refilled.

Engine Air Filter and Cabin Air Filter Maintenance

The engine air cleaner filter should be inspected every 15,000 miles and replaced when needed. Ram sets 30,000 miles or 24 months as the maximum service interval for the engine air filter, whichever comes first.

Trucks used on dusty roads, construction sites or off-road may need an inspection sooner. Dirt and debris in the air cleaner housing should also be removed when the filter is replaced. A diesel engine moves a lot of air when it is working, so this is a cheap place to avoid being cheap.

Air Filter Intervals

Engine air cleaner filter: Inspect every 15,000 miles. Replace when necessary and no later than 30,000 miles or 24 months.

Cabin air filter: Replace every 12,000 miles.

The cabin air filter cleans the air entering the passenger compartment through the heating and air conditioning system. Dust, pollen and road debris eventually restrict airflow through the filter, which can reduce HVAC performance.

Chicagoland construction dust, road salt and seasonal debris can load either filter faster than mileage alone suggests. Visible dirt, reduced airflow or operation in unusually dusty conditions are good reasons to inspect them frequently.

Tire Rotations and Routine Inspections

Ram schedules tire rotations, front-end service and CV or universal-joint inspections every 7,500 miles on a 2026 Ram 2500 or Ram 3500 diesel. Regular inspections matter on a heavy-duty truck because towing, payload and rough roads can turn a small wear issue into an expensive one fairly quickly.

Tire pressure and tread wear should also be checked at every oil change. Ram recommends rotating the tires sooner when irregular wear appears, even when the truck has yet to reach the next scheduled rotation.

Routine Inspection Schedule
Interval Inspection or Service
Every 7,500 miles Rotate the tires, inspect the CV and universal joints and inspect the front end. Lubricate serviceable front-end fittings when equipped.
Every 15,000 miles Inspect the front suspension, tie rod ends and boot seals for cracks, leaks, looseness, wear or damage.
Every 22,500 miles Inspect the brake linings and parking brake operation. Inspect the drive belt and replace worn components as needed.
Every 30,000 miles Inspect the wheel bearings.

Checks to Make Between Scheduled Services

Once a month or before a long trip, Ram recommends checking the engine oil level, battery connections, brakes, steering and suspension components, axle boots, coolant level, lights, wipers and washer fluid.

At each oil change, the truck should also receive an exhaust-system inspection, tire-pressure and tread check, battery inspection, brake inspection, cooling-system hose inspection and front-end inspection. Power side steps and bed steps should be cleaned and lubricated when equipped.

Ram 3500 dual-rear-wheel trucks require extra attention during tire rotation because some wheel positions and tire designs have specific placement requirements. Correct rotation protects tire life and keeps the pressure-monitoring system reporting the proper wheel locations.

Frequently Asked Questions About 2026 Ram 2500 and 3500 Diesel Maintenance

How often does a 2026 Ram 2500 or 3500 diesel need an oil change?

Ram sets the maximum interval at 15,000 miles, 12 months or 500 engine hours, whichever comes first. The truck's oil life system may call for service sooner based on towing, idling, short trips and other operating conditions.

Does Ram have a separate severe-duty oil change interval?

Ram does not publish a separate fixed mileage interval for severe-duty oil changes. The oil life system accounts for how the truck is used and may request service before the 15,000-mile maximum.

How often should the fuel filters be replaced on a 6.7L Cummins?

Both engine-mounted fuel filters should be replaced every 15,000 miles. Both filters should meet Ram's filtration and water-separation requirements.

What should I do if the Water In Fuel light comes on?

Shut the engine off and drain the water from both fuel filters. Starting the engine while water remains in the fuel system can cause damage. If the warning stays on after the filters are drained, schedule an inspection at our North Aurora Truck Repair Center.

How do I know when my Ram diesel needs DEF?

The DEF gauge in the instrument cluster shows the current level. Refill the tank before the warning messages begin escalating and stop filling at the first automatic shutoff.

Is DEF the same thing as the diesel particulate filter?

No. DEF is fluid used by the Selective Catalytic Reduction system. The diesel particulate filter traps soot from the exhaust. Our DPF vs. DEF maintenance guide explains how the two systems work.

How often should the engine air filter be replaced?

Inspect the engine air filter every 15,000 miles. Replace it when needed and no later than 30,000 miles or 24 months. Dusty roads, construction sites and off-road use may require earlier replacement.

When should the transmission and transfer case fluid be changed?

The standard schedule calls for automatic transmission fluid and 4x4 transfer case fluid changes at 60,000 and 120,000 miles. Frequent towing, fleet use and other heavy-duty operation can require earlier transfer case service.

Where can I schedule maintenance for my 2026 Ram diesel?

You can schedule a Ram diesel service appointment with River Front online.

Is River Front part of the Gerald Auto Group?

River Front Chrysler Jeep Dodge Ram is independently owned and is not part of the Gerald Auto Group. We share the North Aurora Auto Mall area with Gerald dealerships, which is why some people refer to us as Gerald Jeep or associate the two businesses.

Keith Sponburgh - River Front Chrysler Jeep Dodge Ram
About the author
Keith Sponburgh
Keith Sponburgh has worked in the automotive industry since 2006. Before joining River Front Chrysler Jeep Dodge Ram, he led eCommerce and sales and service operations for multi store dealer groups across the Chicago area. He has worked on both sides of the desk, in sales and in service, and understands how pricing, trade values, and dealership processes actually work behind the scenes. An Army veteran and former police officer, Keith brings a disciplined, systems driven approach to communication and customer experience. His buyer guides and service content focus on clear information, transparent pricing, and the practical questions people ask when they are deciding what to buy and where to buy it.