A cold air intake on a Duramax is one of the easiest bolt-on upgrades you can do. At stock power levels the gains are modest (5–10 hp), but the real benefit shows up at higher power levels where the factory airbox becomes restrictive — and it reduces EGTs under load.
WHY INTAKE MATTERS ON DIESEL
- More air = more fuel burned = more power (with tuning)
- Better filtration = longer injector life
- Reduced restriction = lower EGTs at WOT
- The factory airbox is not terrible but a well-designed CAI does measurably better
LBZ / LMM INTAKES
- S&B Cold Air Intake: Most popular for LBZ and LMM — includes washable/oiled filter, sealed box
- K&N Intake: Good alternative, slightly simpler design
- aFe Power Momentum HD: Premium option, excellent airflow and filtration
LML INTAKES
- aFe Power Momentum HD is excellent on LML — designed around stock inlet location
- S&B makes an LML-specific kit with a sealed cold-air box
FILTER MAINTENANCE
- Oiled filters need cleaning every 25,000–50,000 miles
- Use the manufacturer’s cleaning kit — not dish soap
- Over-oiling causes MAF sensor contamination on gas trucks; less concern on diesel
- Dry filters (Donaldson, similar) are maintenance-free but less airflow