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.
The 40% Spike in Diesel Emissions Failures
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.
What Causes High Diesel Emissions and MOT Failure?
- →Dirty fuel injectors Poor spray patterns from contaminated injectors cause incomplete combustion, generating more soot and smoke than a clean engine would produce from the same fuel
- →Combustion chamber carbon deposits Carbon build-up from extended service intervals reduces combustion efficiency and increases particulate emissions
- →Contaminated EGR valve A dirty EGR valve affects the air/fuel mixture going into the combustion chamber, reducing combustion quality
- →Damaged or blocked DPF A DPF that cannot filter or regenerate correctly will produce visible smoke — automatic failure
- →Wrong engine oil DPF vehicles require low SAPS oil — standard oil leaves ash deposits in the DPF that cannot be removed during regeneration
What Does Forte Diesel Emissions Reducer Contain and How Does It Work?
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.
- ✓Cleans injectors and combustion chamber Restoring spray patterns and combustion quality means less soot and smoke from the same fuel
- ✓Cleans fuel system, combustion chamber and exhaust Removes deposits that cause incomplete combustion and increased emissions
- ✓Reduces smoke opacity Directly targets the measure used in the diesel smoke opacity test at MOT
- ✓Improves engine performance and response A beneficial side effect of cleaner combustion and a cleaner fuel system
How Long Before My MOT Should I Add Forte Diesel Emissions Reducer?
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:
- ✓Flush the engine with Forte Motor Flush and change the oil Clean oil produces less blow-by and less combustion contamination
- ✓Change the oil filter and air filter A blocked air filter reduces combustion oxygen and increases emissions
- ✓Use correct low SAPS oil if your vehicle has a DPF Standard oil ash deposits in the DPF cannot be removed during regeneration
- ✓Use Forte Advanced Formula Diesel Treatment alongside Cleans injectors and EGR valve — addressing the root causes of poor combustion
Is Forte Diesel Emissions Reducer Worth It?
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.
Every question about
Forte Diesel Emissions Reducer, answered.
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.
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.
- →Forte Advanced Formula Diesel Treatment Cleans injectors, EGR valve and all 10 diesel system components — addresses the root causes of emissions failure
- →Forte Advanced Formula Motor Flush Change the oil before your MOT — clean oil produces cleaner combustion and less contamination
- →Forte DPF Cleaner & Regenerator If the DPF is loaded with soot — lowers burn temperature to help regeneration complete before the test
Use alongside these products.
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.
How to reduce diesel smoke before an MOT retest
A high smoke opacity diesel MOT result usually means the exhaust plume contains too much soot during the acceleration test. Forte Diesel Emissions Reducer is useful when that soot is being driven by contamination: dirty injectors, poor spray pattern, combustion chamber deposits or exhaust aftertreatment deposits that make the fuel burn less cleanly.
For a retest, add Forte Diesel Emissions Reducer to a full tank and drive 100-200 miles before the appointment. That timing matters because you are trying to change what happens during those miles. You want treated fuel circulating through the fuel system long enough to clean deposits and improve combustion quality, not just poured in on the morning of the test.
What to check first
Check the MOT failure sheet, any stored fault codes, obvious service neglect and whether the engine is being given enough driven mileage for the treatment to circulate. A chemical cleaner works best when contamination and deposit build-up are the problem.
When the product helps
It fits smoke and emissions failures linked to fuel-system contamination, heavy particulate build-up, high smoke opacity and dirty combustion. Using it alongside Forte Advanced Formula Diesel Treatment gives broader injector and EGR cleaning before the retest.
When it cannot be the whole fix
SCR/AdBlue-specific faults are not its main job. If the problem is not contamination or deposit build-up, treat the additive as support rather than the whole repair.
Next step before retest
Use the product with enough mileage, avoid short idle-only running, and arrive with the engine fully warm. If the failure sheet shows very high opacity or repeated aborts, pair the clean with proper checks before spending money on parts.
When diesel emissions cleaner can help a fault code
Forte Diesel Emissions Reducer is most relevant where a fault code is being aggravated by dirty combustion and soot load upstream. Cleaner combustion means less soot and particulate output entering the diesel oxidation catalyst, DPF and wider aftertreatment system.
It is less relevant where the code is not being driven by contamination, deposit build-up, soot load or dirty combustion. SCR/AdBlue-specific faults are also not the main job of this product. In those cases, the cleaner may reduce soot output, but it should not be treated as a guaranteed code fix.
Diesel catalyst efficiency
On a diesel, this usually points at catalyst efficiency or catalyst monitoring. The product can help when dirty combustion and soot output are aggravating the aftertreatment system. It is less suitable where contamination is not the cause.
DPF pressure fault
These codes relate to DPF differential pressure readings. If soot load and poor regeneration are part of the cause, reducing soot at source is useful. If cleaning and driving time do not change the problem, treat it as a DPF-system diagnosis rather than repeating additive.
EGR flow contamination
EGR faults often sit alongside smoky diesel running because carbon contamination changes air flow and combustion quality. Forte Advanced Formula Diesel Treatment is the better linked product for EGR cleaning, used alongside this emissions reducer.
SCR and AdBlue limits
Cleaner combustion can reduce the load on the SCR system, but AdBlue crystallisation and SCR-specific faults are not the main job of this product. For AdBlue crystal issues, use the dedicated Forte Exhaust Crystal Preventer page.
The practical order
Read the MOT failure sheet or scan result first. If the problem is smoke opacity, soot load or dirty-combustion symptoms, clean the fuel system and give it 100-200 miles. If the issue points away from contamination, or towards SCR/AdBlue-specific causes, use cleaning as support only and investigate that system before expecting the warning light to stay away.
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.
Clements Trading Ltd
82a James Carter Road
Mildenhall, Bury St Edmunds
Suffolk, IP28 7DE
BMW Tool Rental
63 Purcell Avenue
Lichfield
Staffordshire, WS13 7PH
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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