Cummins 3975818 — Genuine Engine Oil Cooler Core for ISB 6.7L

MPN: 3975818  |  Also Known As: oil cooler core, stacked-plate oil cooler  |  Cross-Refs: 3902372, 3902434, 3903375

Genuine Cummins oil cooler core engineered to stabilize oil temperature and protect bearings, cam, and turbo on ISB 6.7L platforms. Direct-fit for 2007.5–2024 Ram 6.7L. Sold individually (1 per engine).

Features & Benefits

• OE heat rejection for consistent viscosity and stable oil pressure.
• Drop-in replacement for ISB 6.7L with OEM sealing interfaces.
• Stacked-plate core for efficient thermal transfer and durability.
• Prevents bearing/turbo damage from overheated or contaminated oil.
• Built to Cummins standards for fit, function, and long service life.

Verified Fitment (Automotive)

Industrial/Off-Highway: ISB6.7/QSB6.7, especially EPA13+ variants—verify by ESN before ordering.

Specifications

• Type: Engine oil cooler core (stacked-plate)
• OE Part Number: 3975818
• Cross-References (identification): 3902372, 3902434, 3903375
• Quantity Required: 1 per engine (sold individually)

Often Paired With

• Oil cooler gaskets/seals: 3974127 (cooler-to-filter) · 2830559 (cooler-to-block)
• Fresh oil & filter: replace after cooler change to flush debris

What’s In The Box

• (1) Genuine Cummins Oil Cooler Core (3975818)
• Gaskets/hardware sold separately (see “Often Paired With”).

Installation Tips

• Inspect/flush the lubrication circuit after any internal failure before installing the new cooler.
• Use new gaskets and torque fasteners to factory spec; check for leaks on warm-up.
• Change engine oil & filter after installation and again after initial heat cycle if contamination was present.

FAQ

Will this fit my 6.7L Cummins Ram?

Yes—3975818 is the OE cooler for most 2007.5–2024 Ram 6.7L ISB 2500/3500 applications (confirm by VIN/ESN).

Does this come with gaskets?

No—gaskets are sold separately. Common choices are 3974127 (cooler-to-filter) and 2830559 (cooler-to-block).

What about older 5.9L trucks?

Use 3959031 for 2003–2007 5.9L common-rail Rams. 3975818 is the 6.7L cooler.

How do I know my cooler is failing?

Low oil pressure, overheating, or oil/coolant cross-contamination are common signs. Replace promptly to prevent engine damage.

Is this a genuine Cummins part?

Yes—OE Cummins part 3975818 for proper fit and durability.