Every diesel has blow-by. It is the combustion pressure that slips past the rings into the crankcase, and the engine has to vent it. The problem is where the factory sends it. On a stock Cummins, that oily vapor gets routed right back toward the intake. Over thousands of miles it coats the intake tract, builds up sludge, and leaves oil film on everything it touches.
It is not going to grenade your motor tomorrow. But it is a slow buildup that gums up the intake side, makes a mess of the engine bay, and on a built truck it gets a lot worse a lot faster.
What Blow-By Does Over Time
- Coats the intake tract in oil film and sludge
- Leaves oil residue across the top of the engine
- Gets noticeably worse with more power and more cylinder pressure
- Turns into a mess you have to clean instead of one you prevent
The Fix: Catch the Oil Before It Gets There
A catch can does exactly what the name says. It separates the oil out of the crankcase vapor and traps it in a reservoir so it never makes it back to your intake. You empty the can during normal maintenance and your intake stays clean. Our Catch Can Kit for 1998.5 and newer Cummins is a clean, bolt-on setup that handles the vent the way the factory should have from the start.
Who Should Run One
Honestly, every Cummins benefits from one. If you are building power, towing hard, or you just want to keep the intake side clean and the engine bay tidy, a catch can is one of the cheapest upgrades you can make that actually pays you back in less buildup down the road.
Shop the Cummins Catch Can Kit →