What is the Cummins X12?
The X12 is a Cummins diesel engine family used in truck applications. Cummins’ truck body-builder material lists X12 separately from its larger X15 range. Its published ratings depend on the application and generation, so a fire-apparatus or motorhome rating should not be assumed to apply to a freight truck.
What matters in a comparison
When comparing X12 and X15-powered chassis, establish what the actual work requires: operating weight, route, auxiliary equipment and powertrain approval. A smaller engine can change a complete chassis specification, but it does not guarantee a particular fuel or payload saving. Obtain the truck-specific rating sheet and build an ownership comparison around documented operating records.
Fluids & filters
EPA 2017 X12 CM2350, as covered by Cummins QRG 5600647 (revision 10/2024).
Reference checked:
Identify the unit first
Use these details to match the manufacturer's application record before choosing a fluid or ordering a filter.
- Truck VIN
- Engine model and serial number
- Engine emissions/model year
- Installed filter-housing model and original part number
- Factory coolant label and subsequent coolant-change records
Fluid specifications
Engine oil
SAE 10W-30 or 15W-40 meeting the applicable Cummins oil specification.
X12 CM2350 QRG; it does not specify the CES number. Obtain the serial-specific approval and climate grade from QuickServe.
Source 1 ↗Engine coolant
Fully formulated coolant meeting Cummins CES 14603; the guide recommends a 50/50 water/antifreeze mixture or suitable premix.
X12 CM2350. Confirm the product actually meets CES 14603 and matches the installed coolant; ASTM D6210 alone is not sufficient evidence for every formulation.
Source 1 ↗Filter numbers & cross-references
A catalogue cross-reference links part numbers. It does not confirm that either part fits every version of this model. Match the original part to the unit first, then check the replacement manufacturer's application and any supersession.
Engine oil filter
First identify this exact original part through the OEM lookup for your engine serial number and VIN. The X12 CM2350 QRG identifies LF14000NN as the preferred oil filter. The catalogue cross-reference alone does not confirm fitment on every engine in this family.
Application not established by this cross-reference. Confirm this original part number in the manufacturer’s parts catalogue for the exact model and serial number before considering an alternate.
Source 1 ↗ Source 2 ↗Manufacturer catalogue cross-references
- Donaldson P559000Check catalogue ↗
Engine-mounted pressure fuel filter
First identify this exact original part through the OEM lookup for your engine serial number and VIN. The X12 CM2350 QRG identifies FF5825NN; suction-side filters depend on the truck manufacturer’s housing. The catalogue cross-reference alone does not confirm fitment on every engine in this family.
Application not established by this cross-reference. Confirm this original part number in the manufacturer’s parts catalogue for the exact model and serial number before considering an alternate.
Source 1 ↗ Source 2 ↗Manufacturer catalogue cross-references
- Donaldson DBF6776Check catalogue ↗
Cummins parts catalog — identify the engine serial number ↗
Cummins QuickServe — serial-specific service information ↗
What still needs unit-specific confirmation
- Confirm current part supersessions and vehicle-specific fitment through the OEM before ordering. Quantities, capacities and maintenance intervals require the serial-specific manual.
- The chassis-mounted fuel/water separator needs the actual housing make and model.
Official service and parts references
Source 1 ↗ Source 2 ↗ Source 3 ↗ Source 4 ↗Follow the current manufacturer's manual for the identified unit. This page does not set a drain interval, fill quantity or repair procedure.
Questions to take to the supplier
- Is the rating from the truck’s own application?
- Which engine serial number and generation are recorded?
- What transmission and gross combination limits apply?
Sources & limits
Manufacturer material supports the identification and overview above. Comparison considerations and supplier questions are Truck University’s original editorial interpretation, prepared with AI assistance. They are not an independent performance test or expert inspection.
Model-family reference only. Availability, specifications and service requirements can differ by year, market and configuration. Verify the actual vehicle or component using its identification and current manufacturer documentation. Do not use this page as a parts-fitment, modification, repair or loading instruction.
Published specifications and examples retain their labelled units; the header preferences apply to calculators.
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