Diesel Emissions Reducer

Forte Diesel Emissions Reducer

Failed your
diesel MOT
emissions test?

Before you panic — there's something you can do. Forte Diesel Emissions Reducer cleans the complete diesel fuel system, from injectors to exhaust aftertreatment, for cleaner combustion and less smoke. Add it 100-200 miles before your retest.

Order — £20 → How it works
★★★★★
£20 · Free UK delivery · Add 100-200 miles before your MOT
Forte Diesel Emissions Reducer bottle — diesel fuel additive to help pass MOT emissions test
Do you need Forte Diesel Emissions Reducer?
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Failed diesel MOT emissions test
Any diesel with a DPF automatically fails if smoke of any colour is visible. Older diesels without a DPF face stricter opacity limits than before 2018. Forte Diesel Emissions Reducer helps reduce emissions before the retest.
Add immediately — retest in 100-200 miles
📅
MOT due and worried about emissions
If your diesel produces visible smoke or you know the injectors or EGR valve are dirty, use Forte Diesel Emissions Reducer preventatively before your MOT. Add 100-200 miles before the test date.
Add now — drive 100-200 miles before test
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Want to maintain low emissions year-round
Used at every service alongside Forte Advanced Formula Diesel Treatment, Forte Diesel Emissions Reducer helps maintain low emissions consistently — not just before the MOT.
Use at every service
The scale of the problem

The 40% Spike in Diesel Emissions Failures

Diesel MOT emissions failures increased dramatically after stricter rules were introduced. The rules changed — but many vehicles and their owners were not ready for them.

In May 2018 the UK MOT test was updated with significantly stricter diesel emissions requirements. Any diesel vehicle fitted with a DPF automatically fails if smoke of any colour is visible from the exhaust during the test. Older diesels without a DPF now face lower opacity limits than before.

The result was an immediate spike in diesel failures. Almost 1.3 million vehicles failed their MOT on emissions grounds in 2020 alone. Many of these were vehicles that had passed without issue in previous years — until the rules changed.

The good news is that many emissions failures are caused by dirty injectors, combustion chamber deposits and EGR contamination — all of which respond to chemical treatment before the test.

The 40% spike in diesel emissions failures — showing the increase in diesel MOT failures after stricter emissions rules were introduced in 2018, with almost 1.3 million vehicles failing on emissions in 2020
1.3M
Vehicles failed MOT on emissions
In 2020 alone — making emissions one of the most common MOT failure reasons
2018
Stricter rules introduced
May 2018 — automatic fail for any visible smoke from DPF-equipped diesels
0
Smoke tolerance for DPF vehicles
Any smoke of any colour means automatic failure for diesel vehicles fitted with a DPF
Root causes

What Causes High Diesel Emissions and MOT Failure?

Most diesel emissions failures are not caused by a broken engine — they are caused by a dirty one. Contamination that has built up over time changes combustion quality and increases the particulates and smoke that cause failure.
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    Dirty fuel injectorsPoor spray patterns from contaminated injectors cause incomplete combustion, generating more soot and smoke than a clean engine would produce from the same fuel
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    Combustion chamber carbon depositsCarbon build-up from extended service intervals reduces combustion efficiency and increases particulate emissions
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    Contaminated EGR valveA dirty EGR valve affects the air/fuel mixture going into the combustion chamber, reducing combustion quality
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    Damaged or blocked DPFA DPF that cannot filter or regenerate correctly will produce visible smoke — automatic failure
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    Wrong engine oilDPF vehicles require low SAPS oil — standard oil leaves ash deposits in the DPF that cannot be removed during regeneration
Diagnosing the root causes of visible exhaust smoke — showing the main causes of diesel emissions MOT failure including dirty injectors, combustion chamber deposits, contaminated EGR valve, damaged DPF and incorrect oil type
How Forte Diesel Emissions Reducer cleans the diesel fuel system, combustion chamber and exhaust aftertreatment to reduce black smoke and exhaust emissions
How it works

What Does Forte Diesel Emissions Reducer Contain and How Does It Work?

Forte Diesel Emissions Reducer cleans the complete diesel fuel system — supporting cleaner, more complete combustion and reducing the smoke and particulates that cause MOT failure.

It works right through the system — injectors, combustion chamber and exhaust aftertreatment. As the treated fuel passes through, it cleans the deposits that cause poor injector spray patterns and incomplete combustion. Cleaner injectors and a cleaner combustion chamber mean fuel burns more completely — less unburnt fuel, less soot and less black smoke.

As the treated fuel travels through the system it also cleans the fuel system, combustion chamber and exhaust — reducing the deposits that cause incomplete combustion in the first place. The combined effect is reduced particulate output and reduced smoke opacity — the two measures that most commonly cause diesel MOT failure.

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    Cleans injectors and combustion chamberRestoring spray patterns and combustion quality means less soot and smoke from the same fuel
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    Cleans fuel system, combustion chamber and exhaustRemoves deposits that cause incomplete combustion and increased emissions
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    Reduces smoke opacityDirectly targets the measure used in the diesel smoke opacity test at MOT
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    Improves engine performance and responseA beneficial side effect of cleaner combustion and a cleaner fuel system
When to use it

How Long Before My MOT Should I Add Forte Diesel Emissions Reducer?

Add to a full fuel tank 100-200 miles before your MOT test. This gives the product enough time to travel through the entire system and begin cleaning combustion deposits before the test.

The product needs to travel through the fuel system and the engine needs to run on the treated fuel for some miles before the full benefit is seen. Too close to the test and the product has not had time to clean through. 100-200 miles of normal driving gives a good balance.

For best results before the MOT also:

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    Flush the engine with Forte Motor Flush and change the oilClean oil produces less blow-by and less combustion contamination
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    Change the oil filter and air filterA blocked air filter reduces combustion oxygen and increases emissions
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    Use correct low SAPS oil if your vehicle has a DPFStandard oil ash deposits in the DPF cannot be removed during regeneration
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    Use Forte Advanced Formula Diesel Treatment alongsideCleans injectors and EGR valve — addressing the root causes of poor combustion
The pre-MOT treatment timeline — showing the recommended schedule for using Forte Diesel Emissions Reducer before a diesel MOT test, including when to add the product, change oil and filter, and what else to do to maximise the chance of passing
Prevention versus cure

Is Forte Diesel Emissions Reducer Worth It?

Yes — but the better question is whether you should be using it reactively before your MOT or preventatively at every service. Prevention is always more effective than cure.

Used reactively before a failed MOT, Forte Diesel Emissions Reducer can help reduce emissions enough to pass a retest — but the underlying causes of those high emissions have not been resolved. The injectors are still dirty. The EGR valve is still contaminated. The next MOT will present the same problem.

Used preventatively at every service alongside Forte Advanced Formula Diesel Treatment, it keeps emissions consistently low year-round. The MOT becomes a formality rather than a risk. And the engine runs more cleanly, more efficiently and with less wear in between services.

At £20 with free UK delivery, it costs a fraction of an MOT retest fee, a garage diagnostic or a forced regeneration — and far less than an injector, EGR or DPF repair. For most diesels it is the cheapest first thing to try.

The paradigm shift prevention versus cure — showing how using Forte Diesel Emissions Reducer preventatively at every service maintains consistently low emissions year-round, versus the reactive approach of only treating before a failed MOT
Common questions

Every question about
Forte Diesel Emissions Reducer, answered.

My car failed its MOT on emissions — what can I do?
You usually have 10 working days to retest. Before the retest: add Forte Diesel Emissions Reducer to a full fuel tank and drive 100-200 miles, change the oil and filter (low SAPS oil if you have a DPF), check the air filter, and add Forte Advanced Formula Diesel Treatment to clean the injectors and EGR valve. Most emissions failures come from dirty injectors and combustion deposits — which respond to chemical cleaning before the retest.
How much does it cost to fix diesel emissions before a retest?
It depends on the cause. If it's dirty injectors and combustion deposits, a bottle of Forte Diesel Emissions Reducer plus an oil and filter change is the cheapest first step — far less than a garage diagnostic, a forced DPF regeneration, or replacing an injector, EGR valve or DPF. Start with the low-cost chemical clean before paying for parts.
What's the best additive to reduce diesel emissions?
Use one that cleans the whole fuel system rather than masking the symptom. Forte Diesel Emissions Reducer cleans the injectors, combustion chamber and exhaust aftertreatment to support cleaner, more complete combustion and reduce black smoke. Used with Forte Advanced Formula Diesel Treatment it tackles the dirty injectors and EGR contamination behind most emissions failures.
How do I fix black smoke from my diesel — and does a DPF stop it?
Black smoke is unburnt fuel from incomplete combustion — usually dirty injectors, combustion deposits or a contaminated EGR valve. A working DPF traps much of the soot, but if it's blocked or combustion is poor, smoke still shows. Cleaning the fuel system with Forte Diesel Emissions Reducer and Forte Advanced Formula Diesel Treatment reduces soot at source; a soot-loaded DPF can be helped with Forte DPF Cleaner & Regenerator.
What causes high emissions on a diesel car?
The common causes are dirty fuel injectors producing incomplete combustion, carbon build-up in the combustion chamber, a contaminated EGR valve, a blocked or poorly regenerating DPF, and the wrong (non-low SAPS) oil in a DPF vehicle. Most are contamination problems that respond to chemical cleaning rather than mechanical repair.
Can I use it with Forte Advanced Formula Diesel Treatment?
Yes — and we recommend it. Add both to a full fuel tank together. Forte Advanced Formula Diesel Treatment cleans all 10 diesel system components including the injectors and EGR valve, while Forte Diesel Emissions Reducer cleans the fuel system, combustion chamber and exhaust aftertreatment. Together they address both the root cause and the immediate emissions symptom.
My diesel doesn't have a DPF — will it still help?
Yes. Older diesels without a DPF are tested on smoke opacity, and the limits were tightened in 2018. Failure is usually caused by dirty injectors and combustion deposits, which Forte Diesel Emissions Reducer cleans to reduce opacity. If the cause is mechanical wear rather than contamination, chemical cleaning will help less.
Diagnostic trouble codes

Emissions fault codes linked
to dirty diesel combustion

If your diesel has thrown one of these codes — or the garage flagged it before the MOT — it often points to the same root causes Forte Diesel Emissions Reducer and Forte Advanced Formula Diesel Treatment address: incomplete combustion, soot loading and a contaminated EGR or DPF. Codes that indicate mechanical failure or a faulty sensor need diagnosis first.

P2002 / P2463
DPF efficiency below threshold / soot accumulation. The filter is loaded with soot and struggling to regenerate — a leading cause of visible smoke and emissions failure. Pair with Forte DPF Cleaner & Regenerator.
P244A / P244B
DPF differential pressure too low / too high. The pressure sensor is reporting a blocked or poorly regenerating filter — reducing the soot load helps the readings return to normal.
P0401 / P0402
EGR flow insufficient or excessive. A carbon-clogged EGR valve upsets the air/fuel mixture and combustion quality. Forte Advanced Formula Diesel Treatment cleans the EGR circuit.
P0420 / P0430
Catalyst (DOC) efficiency below threshold. The diesel oxidation catalyst is not converting emissions effectively, often because combustion is dirty and soot-laden upstream.
P20EE / P204F
SCR / NOx catalyst efficiency below threshold (AdBlue systems). Cleaner combustion lowers the NOx load the SCR system has to handle, though a faulty dosing system needs separate diagnosis.
P0201–P0204
Injector circuit faults, cylinders 1–4. Worn or fouled injectors cause poor spray patterns, incomplete combustion and excess smoke. Clean injectors with Forte Advanced Formula Diesel Treatment.

Failed your MOT?
Add it now.
Retest in 100-200 miles.

Forte Diesel Emissions Reducer cleans the complete diesel fuel system to support cleaner combustion and reduce the black smoke and emissions that cause diesel MOT failure. Free UK delivery.

£20free UK delivery
Order Forte Diesel Emissions Reducer — £20 →
Use alongside these products for best results
Complete diesel system maintenance

Use alongside these products.

Add to fuel tank alongside
Forte Advanced Formula Diesel Treatment
Cleans all 10 diesel system components — injectors, EGR valve, combustion chamber and more. Use alongside Forte Diesel Emissions Reducer to address the root causes of emissions failure, not just the symptom.
View Forte Advanced Formula Diesel Treatment →
For DPF-related failures
Forte DPF Cleaner & Regenerator
If the DPF is loaded with soot and unable to regenerate, Forte DPF Cleaner & Regenerator lowers the soot burn temperature to help regeneration complete — reducing the soot load before your MOT.
View Forte DPF Cleaner & Regenerator →
Change oil before your MOT
Forte Advanced Formula Motor Flush
Flushing the engine and changing the oil before your MOT is good practice. Clean engine oil produces less combustion contamination and gives Forte Diesel Emissions Reducer the cleanest possible environment to work in.
View Forte Advanced Formula Motor Flush →

Take A Look At Our 5 Star Reviews For Forte Seal Conditioner

At BMW Tool Rental, we pride ourselves on providing excellent customer service and offering honest and reliable advice to our customers. We understand that when it comes to your car, you want to ensure that you are using the right products and getting the right advice. That's why we take the time to listen to our customers, understand their concerns, and provide the best possible solution.

Our forte seal conditioner has received numerous 5-star reviews from our satisfied customers, who have found our product to be effective in reducing engine oil leaks and stopping blue smoke caused by worn valve seals. However, we don't just rely on product reviews to show our commitment to customer satisfaction. We offer a personal touch that sets us apart from other retailers.

If you have any questions about our products or services, we encourage you to reach out to us. We're always happy to help and provide you with the information you need to make the right decision. Whether you're looking to rent our AGA valve seal tool or purchase our forte seal conditioner, we're here to help.

Take A Look At Our 5 Star Reviews For Forte Seal Conditioner

At BMW Tool Rental, we pride ourselves on providing excellent customer service and offering honest and reliable advice to our customers. We understand that when it comes to your car, you want to ensure that you are using the right products and getting the right advice. That's why we take the time to listen to our customers, understand their concerns, and provide the best possible solution.

Our forte seal conditioner has received numerous 5-star reviews from our satisfied customers, who have found our product to be effective in reducing engine oil leaks and stopping blue smoke caused by worn valve seals. However, we don't just rely on product reviews to show our commitment to customer satisfaction. We offer a personal touch that sets us apart from other retailers.

If you have any questions about our products or services, we encourage you to reach out to us. We're always happy to help and provide you with the information you need to make the right decision. Whether you're looking to rent our AGA valve seal tool or purchase our forte seal conditioner, we're here to help.

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Lichfield
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Lichfield
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Clements Trading Ltd trading as BMW Tool Rental. Registered in England & Wales, company no. 10629836. Registered office: 82a James Carter Road, Mildenhall, Bury St Edmunds, Suffolk, IP28 7DE.

BMW Tool Rental is an independent specialist supplying tool hire and Forte automotive additives. We are not affiliated with, authorised by, or endorsed by BMW AG. "BMW" is a trademark of BMW AG and is used here for descriptive/compatibility purposes only.

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