6.7 Cummins oil capacity: 12 quarts on pre-2019 trucks, 10 quarts after

The 6.7L Cummins has been in Ram 2500 and 3500 trucks since the 2007.5 model year, and the oil capacity changed once during that run. 2007.5 to 2018 trucks take 12 quarts (11.4 L) with filter. 2019 and later trucks take 10 quarts (9.5 L) with filter. The reduction came with the engine refresh that bumped horsepower to 400 and torque to 1,000 lb-ft.

If you’re servicing an older 6.7 with a service manual that says 12 quarts and then add 12 to a 2020 truck, you’re two quarts over the high mark. Always check the dipstick after filling.

Oil capacity by year

The filter holds roughly half a quart to one quart of oil depending on the design. The numbers above are what comes out of the bottle into the engine after a complete drain and filter swap.

Oil grade: 15W-40 versus 10W-30

Cummins specifies an API CK-4 or CJ-4 rated diesel oil. The viscosity choice depends on climate and use:

• 15W-40: The default Cummins recommendation for hot climates, towing, and heavy-duty work. Used by most owners year-round.
• 10W-30: Approved for normal-duty use, especially in colder climates where 15W-40 is harder to cold-start. Gives slightly better cold-weather flow without losing meaningful protection at temperature.
• 5W-40 synthetic: Approved for severe-duty cold-climate use. More expensive and only worth the spend if you’re starting in sub-zero temperatures regularly.

Don’t run a passenger-car oil. The 6.7’s emissions equipment (DPF, SCR) needs the lower ash content of a CK-4 or CJ-4 oil. Standard “for any engine” oils have ash levels that gradually plug the DPF.

Always confirm the spec on the engine oil bottle says “CK-4” or “CJ-4.” Recent oils are usually CK-4, which supersedes CJ-4 and is backward compatible.

Oil change interval

Ram’s published interval for the 6.7 Cummins is 15,000 miles or 12 months under normal duty, whichever comes first. Under severe duty (frequent towing, idling, dusty conditions, short trips in cold weather) the interval drops to 7,500 miles or 6 months.

In practice, most owners who tow heavy run a 7,500 to 10,000 mile interval. The truck’s oil life monitor adjusts the warning based on driving conditions, so let the warning trigger naturally rather than going by the calendar alone.

The oil change warning resets through the dash menu on most trucks: Settings → Vehicle → Oil Life Reset, or hold the gas pedal to the floor for 10 seconds with the key on (not running) on older trucks. Check the owner’s manual for the exact procedure on your truck.

The right filter

The 6.7 Cummins uses a spin-on cartridge filter on most years. The OEM Mopar part number changed when Cummins refreshed the engine; use the part number listed on your truck’s oil cap or check it against the year on the Mopar parts site.

Aftermarket filters from Fleetguard (Cummins’s own filter brand), Wix, Donaldson, and Baldwin are all reliable. Avoid no-name filters. The 6.7 lifts oil under pressure to a turbocharger that runs over 100,000 rpm; a filter that bypasses internally or collapses under cold-start pressure is how a turbo fails.

What it costs to do it yourself

For a 2019+ truck (10 quarts):

• 3 gallons of 15W-40 CK-4: $40 to $60
• Oil filter: $15 to $25
• Drain plug crush washer: $1 to $2
• Disposal fee at any auto parts store: free

Total around $60 to $90, plus an hour of your time. A dealer change runs $130 to $200 depending on region. Independent diesel shops sit somewhere between.

For a pre-2019 truck (12 quarts), add the cost of two more quarts.

Where the drain plug and filter actually live

The drain plug is on the underside of the oil pan, accessible without lifting the truck on most trims (the running boards may help your reach). It’s a 14mm or 1/2” square-drive plug depending on year. Always use a torque wrench: 27 lb-ft for a steel pan, less for aluminum. Stripped pans are common on trucks where someone “muscled” the plug back in.

The oil filter is on the passenger side of the engine, mounted vertically near the front. It’s accessible from above through the engine bay; you don’t need to crawl underneath. A good filter wrench is worth having because the factory torque on these is high enough that hand-tightening doesn’t break it loose.

Step-by-step oil change

1. Warm the engine for 5 minutes. Cold oil takes 20+ minutes to drain; warm oil drains in 5.
2. Park on level ground, chock the rear wheels, turn off the engine.
3. Lift the hood and pop the oil filler cap to vent the system.
4. Place an oil pan that holds at least 13 quarts under the drain plug. The 6.7 dumps fast and hard once the plug is out.
5. Loosen the drain plug carefully. Once it’s broken free, finish with your fingers and pull it the rest of the way.
6. Let drain for 10 minutes minimum. The last bit always trickles slowly.
7. Replace the crush washer (don’t reuse the old one) and torque the drain plug to spec.
8. Remove the oil filter from above the engine. Catch the residual oil in a rag or small pan.
9. Smear a thin layer of fresh oil on the new filter’s rubber gasket. Spin it on hand-tight, then 3/4 turn more.
10. Add the correct quantity through the filler cap. Pour slowly enough that you don’t overflow the funnel.
11. Start the engine. Let it idle for 30 seconds. Check for leaks at the drain plug and filter.
12. Shut off, wait 5 minutes, check the dipstick. Top off if needed.
13. Reset the oil life monitor.

Checking the dipstick correctly

The 6.7 dipstick has two crosshatched marks. Cold readings are deceiving on a diesel because there’s always some film left in the engine. The accurate way to check oil level:

• Warm the engine, drive it, then park on level ground.
• Wait 5 to 10 minutes after shutoff for oil to drain back to the pan.
• Pull the dipstick, wipe it, reinsert fully, pull it again, read.

The level should sit between the two crosshatch marks. If it’s at or below the bottom mark, you’re a quart low. If it’s above the top mark, you overfilled, which can foam the oil and damage the turbo.

Reading oil analysis

If you want to extend the interval beyond the factory recommendation, send a sample to Blackstone Labs or a similar oil analysis service. They’ll measure wear metals, viscosity, soot loading, and contamination. The 6.7 Cummins typically holds up well for 12,000 to 15,000 miles when not heavily towed, and analysis will tell you whether your specific truck’s oil is still safe to run.

That’s the empirical way to extend intervals. The handwave-it way is to trust forum guesses, which works until it doesn’t and you eat an injector replacement.

When to do an oil and filter change early

A few situations where you should change oil sooner than the interval:

• After a long towing trip (over 1,000 miles fully loaded).
• After significant idling (more than 10 hours of cumulative idle time since the last change).
• After short-trip driving for an extended period (the engine never gets fully warm).
• After any coolant or fuel intrusion event into the oil.
• If the oil smells of fuel or looks milky.

The cost of an extra oil change is around $80. The cost of a worn 6.7 Cummins is north of $15,000 for a rebuild. The math heavily favors the early change.