A crankcase filter delete removes the factory crankcase ventilation filter from your 6.7 Cummins engine
The 6.7 Cummins diesel (used in Ram 2500 and 3500 trucks from 2007 onward) came equipped with a crankcase filter that traps oil mist and particulates from engine blow-by gases before they re-enter the intake. A delete removes this filter entirely and reroutes those gases directly back into the intake manifold or atmosphere, depending on the setup.
This is a mechanical modification, not a software change. It involves removing the factory filter canister, disconnecting hoses, and either capping off the system or installing an aftermarket catch can. The modification is permanent unless you reinstall the original equipment.
Owners pursue this for three main reasons: to reduce backpressure in the crankcase ventilation system, to eliminate the factory filter's maintenance burden, or to lower intake manifold temperatures by venting gases differently. Whether it makes sense for your truck depends on your engine's condition, your driving style, and local emissions rules.
Key Takeaways
- A crankcase filter delete removes the factory filter canister and reroutes blow-by gases, reducing crankcase backpressure but requiring either a catch can or direct atmospheric venting.
- The factory filter on a 6.7 Cummins can clog over time, especially on higher-mileage engines or those running heavy loads, which is why some owners delete it.
- A delete does not improve horsepower or fuel economy on a stock engine, but it may help slightly on modified engines with higher boost or fuel injection changes.
- Deleting the crankcase filter voids the factory warranty and may fail emissions testing in states that require it, so check your local regulations before proceeding.
- If you keep the factory filter, inspect it every 30,000 miles and replace it if it shows oil saturation or restriction; a clogged filter can raise crankcase pressure and damage seals.
How the factory crankcase ventilation system works on the 6.7 Cummins
Diesel engines produce blow-by: combustion gases that slip past the piston rings and accumulate in the crankcase. If these gases are not vented, pressure builds and can blow out seals, gaskets, and the dipstick tube. The factory crankcase ventilation system on the 6.7 Cummins routes these gases through a filter canister, which traps oil and particulates, then sends the cleaned gas back into the intake manifold.
The factory filter is a cartridge-style element housed in a plastic or aluminum canister mounted on or near the valve cover. Hoses connect the crankcase to the filter inlet and the filter outlet to the intake. Over time, the filter element becomes saturated with oil and can restrict flow, raising crankcase pressure. A restricted filter also forces more unfiltered blow-by into the intake, which can foul the intake valves and increase carbon buildup.
On stock 6.7 engines, the factory system works adequately for normal driving. On modified engines with higher boost, larger fuel injectors, or EGR delete kits, blow-by volume increases significantly, and the factory filter may not keep up.
Why owners delete the crankcase filter
The most common reason is to lower crankcase backpressure. Even a clean filter creates some resistance to gas flow. By removing it, you reduce the pressure the engine must overcome to vent blow-by, which can help slightly on heavily modified engines. This is not a horsepower gain on a stock truck, but on a truck with a turbo upgrade or fuel tune, every bit of backpressure reduction can matter.
A second reason is maintenance avoidance. The factory filter must be inspected regularly and replaced when saturated. On a truck that sees heavy towing or frequent idling, this can happen every 30,000 to 50,000 miles. A delete eliminates that task, though it shifts the burden to a catch can if you install one.
A third reason is intake manifold temperature management. Some owners report that venting blow-by gases directly to atmosphere (rather than back into the intake) can lower intake temperatures slightly, which may help on modified engines running aggressive tunes. This effect is modest and depends on your specific setup.
What happens when you delete the crankcase filter
Mechanically, the delete process involves removing the factory filter canister, disconnecting the hoses, and capping or rerouting them. You then choose one of two paths: install an aftermarket catch can, or vent directly to atmosphere.
A catch can is a small reservoir that collects oil and moisture from blow-by gases before they re-enter the intake or exit to air. It requires periodic draining (every 5,000 to 10,000 miles on a modified engine, less often on stock) but keeps oil out of the intake and atmosphere. Many owners view a catch can as the responsible middle ground: you get the backpressure reduction of a delete without the oil vapor entering the engine or the environment.
A direct atmospheric vent sends blow-by gases straight to the air. This is the simplest and cheapest option but means oil mist exits your engine into the atmosphere. It also means no oil re-enters the intake, which some tuners prefer for cleaner combustion. However, this approach is illegal in most states for on-road vehicles and will fail emissions testing.
Warranty, emissions, and legal considerations
Deleting the crankcase filter voids your factory warranty on the engine and related systems. Dodge and Cummins will not cover failures if they discover the modification. If your truck is still under warranty and you plan to keep it that way, a delete is not an option.
Emissions testing varies by state. States that perform OBD-II (on-board diagnostic) testing may flag a delete if the truck's computer detects a missing or disconnected sensor. States that perform tailpipe testing may not catch a delete directly, but if you vent to atmosphere, the visible oil mist can fail a visual inspection. Check your state's specific emissions rules before proceeding.
On federal lands and in some jurisdictions, modifying the crankcase ventilation system on a diesel truck is prohibited. If you tow or travel in national forests or BLM areas, verify the rules for your region.
Catch can versus direct vent: which route makes sense
A catch can is the more practical choice for most owners. It preserves the backpressure reduction benefit of a delete, keeps oil out of the intake (which is cleaner for a tuned engine), and is legal in all states. The trade-off is that you must drain it regularly and it adds a small cost upfront.
Direct atmospheric venting is cheaper and requires no maintenance, but it is illegal for on-road use in most places and will fail emissions. It is sometimes used on dedicated off-road or race trucks where emissions compliance is not a concern.
If you are undecided, start with a catch can. You get the benefits of a delete without the legal and environmental downsides. If you later decide the modification is not for you, you can reinstall the factory filter and remove the catch can.
Maintenance of the factory filter if you keep it
If you decide not to delete, proper maintenance of the factory filter is important. Inspect the filter element every 30,000 miles. If it is dark, wet, or feels heavy with oil, replace it. On a truck that tows frequently or idles a lot, you may need to replace it more often.
A clogged factory filter raises crankcase pressure, which can damage the valve cover gasket, push oil past the dipstick tube seal, or blow out the rear main seal over time. Replacing the filter is cheap insurance against these failures. Replacement filters for the 6.7 Cummins are widely available and cost between $30 and $80 depending on the brand.
If you notice oil mist or smoke around the valve covers, or if your crankcase pressure gauge (if you have one) reads high, the filter may be clogged. Replace it before the pressure damages seals.
Frequently Asked Questions
Will a crankcase filter delete add horsepower to my 6.7 Cummins?
Not on a stock engine. The backpressure reduction is minimal on a factory truck. On a modified engine with a turbo upgrade or fuel tune, a delete may contribute a small amount to overall gains, but it is not a standalone power modification. Most of the benefit is in reducing crankcase pressure, which helps the engine breathe more freely under load.
Can I delete the crankcase filter and still pass emissions testing?
It depends on your state and how you delete. If you install a catch can and keep the system closed (no atmospheric venting), you may pass OBD-II testing. If you vent to atmosphere, you will likely fail both OBD-II and visual inspections in states that require emissions compliance. Check your state's specific rules before modifying.
How often do I need to drain a catch can?
On a stock 6.7 Cummins, every 10,000 to 15,000 miles is typical. On a modified engine with higher boost or fuel injection, you may need to drain it every 5,000 miles. Some owners check it every oil change and drain as needed. The frequency depends on how much blow-by your engine produces.
What happens if I delete the crankcase filter without a catch can?
Oil mist and moisture will vent directly to the atmosphere or intake, depending on your setup. If vented to air, you will see visible oil mist around the engine and fail emissions testing. If routed to the intake, oil will foul the intake valves and increase carbon buildup over time. A catch can is strongly recommended if you delete.
Does a crankcase filter delete void my warranty?
Yes. Any modification to the crankcase ventilation system is considered a non-factory alteration, and Dodge and Cummins will not cover engine or related system failures if the modification is discovered. If your truck is under warranty and you want to keep it that way, do not delete the filter.