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Perkins DEF Filters
A Perkins DEF filter is an aftertreatment filter, not an engine filter. It cleans Diesel Exhaust Fluid (urea / AdBlue) before it is injected into the SCR system, protecting the dosing unit and the catalyst — and it is separate from the fuel, oil, air and coolant filters covered by the engine-service scope. Before any number is quoted, the engine build and the fitted filter have to be identified.
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Perkins DEF Filter References
Two Perkins DEF filter numbers are listed as product references. Confirm the engine build before treating either number as the part your engine carries.
DEF / SCR Aftertreatment
Perkins 4951506 DEF Filter
Listed as a DEF filter number for the 1200 Series. Confirm the build before relying on this reference.
DEF / SCR Aftertreatment
Perkins T435902 DEF Filter
A broad-range reference across the 900–2800 Series. Production year and emissions stage can change the arrangement.
What This Page Covers, and What It Does Not
This page covers aftertreatment filtration only: DEF (diesel exhaust fluid / urea / AdBlue) filters for Perkins engines. It is not an SCR-system tutorial, a stock list, a price list, or a fitment certificate.
In Scope: DEF Filtration Only
- DEF / AdBlue / urea filters
- SCR aftertreatment filtration
- 4951506 for 1200 Series
- T435902 across 900–2800 Series
- T400394, T426559, T401178
- ISO 22241-1 fluid compliance
Outside This Page
The Perkins DPF filters page carries the other aftertreatment system, the Perkins fuel filters page carries the engine-service fuel elements, and the Cummins DEF filters page covers the same role on Cummins engines. The Perkins filter range covers the other positions.
Availability is confirmed in the quotation. With the build and the number off the old filter, request a Perkins DEF filter quote.
Confirm the Build,
Then the Number
Then the Number
DEF filtration exists only on Tier 4 Final / Stage IV builds with SCR aftertreatment. Older mechanical builds have no DEF filter at all, which is one reason the build — not the model name — is what determines the part.
DEF Filter vs DPF vs Engine-Service Filtration
A shared number or a thread match is not proof of the right part. Confirm which system the filter serves, then confirm the build.
| Component | System | What It Filters | Engine-Service Filtration? |
|---|---|---|---|
| DEF filter | SCR aftertreatment | Urea / AdBlue fluid before dosing | No — aftertreatment |
| DPF (diesel particulate filter) | Exhaust aftertreatment | Soot from exhaust gas | No — aftertreatment |
| Fuel / oil / air filter | Engine service | Fuel, oil, intake air | Yes |
A DEF filter has nothing to do with engine oil, fuel, intake air or coolant. Those are engine-service filtration, and they are separate systems with separate references.
Replacement Practice and Fluid Quality
Two points decide most DEF filter enquiries: how the element is replaced, and whether the fluid meets specification.
Replacing a Perkins DEF Filter
The cap and element are a combined assembly, replaced as a unit. Perkins service literature describes a threaded cap and element that are replaced together, and the system self-primes on power-up.
The manual’s cautions are to keep the DEF manifold area free of contamination and to purge the DEF lines before filling the tank.
Check the manualThese are the manual’s procedures, not our advice. Do not take a torque figure or a replacement interval from this page; both belong to the specific engine’s manual.
DEF Fluid Quality and the Warranty Caveat
DEF must meet ISO 22241-1. Fluid that does not meet the specification can damage the dosing system and the SCR catalyst. The specification, not the brand, is what matters.
Perkins’ warranty documentation excludes failures caused by non-Perkins fluids and filters. This is the strongest reason to declare a genuine-original requirement up front and to confirm what is being fitted.
Check the termsConfirm the warranty terms that apply to your specific order. This page identifies the filter; it does not supply DEF fluid or prescribe a fluid-handling programme.
Records to Confirm Before You Order
Have these five details ready when you request a quote, whether you need one filter or a service set.
Engine Identification
Engine maker, model, and the full serial or build number. The model name alone does not identify the DEF filter arrangement.
Which System the Filter Serves
DEF / SCR aftertreatment — not engine-service filtration, and not DPF. State the system explicitly.
Complete Filter Part Number
The number printed on the removed DEF filter, and whether it has been superseded. Copy every prefix and suffix.
Original or Alternative
Whether the requirement is for a genuine original or an alternative, declared before quoting so the offer is unambiguous.
Quantity and Service Scope
State the quantity for each item and whether the requirement is one filter or a service set.
Where two records disagree, send both; the difference usually points to a supersession, a build variation, or a filter fitted from the wrong number last time. For the full sequence, see how to identify the correct engine filter.
Where DEF Filter Selection Goes Wrong
Similar housings and familiar references can hide a different application. Review these common mix-ups before confirming an order.
DEF or DPF?
A DEF filter cleans the urea fluid; a DPF traps soot from exhaust gas. Both are aftertreatment, but they are different systems and different parts.
Check the systemConfirm which aftertreatment component is being replaced.
DEF Filter or Fuel Filter?
A DEF filter is aftertreatment — it cleans urea fluid before it reaches the SCR dosing system. A fuel filter is engine-service and cleans fuel before the injection system.
Check the boundaryAftertreatment and engine-service filtration are separate scopes.
Cross-Reference or Confirmed Match?
A reference list narrows the search. It does not by itself establish media, seals, valves or the full application specification.
Check the applicationReview the offered item against the build and the installed arrangement.
Complete or Superseded Number?
An omitted prefix, suffix or changed reference can lead the search in the wrong direction. Keep the complete identification from the removed element.
Check both referencesWhere a number has changed, retain the old and current references for review.
Frequently Asked Questions
Which Perkins DEF filter do I need?
It depends on the engine build, not the model name alone. 4951506, T435902, and other numbers are all Perkins DEF filters for different series and prefixes. Send the build and the old number and we confirm the item.
Is a DEF filter the same as a fuel filter?
No. A DEF filter is aftertreatment — it cleans urea fluid before it reaches the SCR dosing system. A fuel filter is engine-service and cleans fuel before the injection system.
What is the difference between a DEF filter and a DPF?
A DEF filter cleans the urea fluid; a DPF traps soot from exhaust gas. Both are aftertreatment, but they are different systems and different parts.
Does a Perkins engine always have a DEF filter?
No. The DEF filter exists only on Tier 4 Final / Stage IV builds with SCR aftertreatment. Older mechanical builds have no DEF filter, which is why the build is what we confirm.
Can I use an aftermarket Perkins DEF filter?
State the requirement before quoting; any alternative is labelled as one. Confirm the number against the build, and note the warranty covers only Perkins fluids and filters.
Confirm the Build, Then the Number
A Perkins DEF filter is quoted against a system, a build list, and a number, in that order. Send the engine model, the serial or build number, and the number printed on the removed DEF filter — 4951506, T435902, or whatever is fitted. We will confirm which DEF filter the build calls for, state the offered item and the delivery terms line by line.
Request a Perkins DEF Filter Quote →For a whole list across several engines, see bulk filter supply.