Euro 6 diesel engines explained​

Ownership Information and FAQs from Peoples Ford

Ford Dealer in Scotland & Northern England

​Under the new European Union emissions limits, Euro 6, diesel engines are cleaner than ever before. Sophisticated technologies have reduced emissions of gases which are damaging to the environment such as nitrogen oxide and particulate matter.  

Modern diesel engines use innovative technologies to burn less fuel and emit fewer harmful gases than in the past. Emissions from Euro 6 diesel engines are equivalent to those from a petrol engine, with damaging gases such as carbon dioxide and nitrogen oxides reduced significantly.

Here are some of the key elements of engine design which have helped to clean up diesel’s act.

Turbo charger

The turbo charger forces extra air into the combustion chamber, which has the effect of boosting both the power output and the fuel efficiency of the engine.

Common rail

If fuel is injected into the engine at higher pressure it will burn more cleanly and efficiently. The common rail is a high-pressure reservoir of diesel. The fuel is injected from the common rail into the engine in a sequence of pulses just milliseconds apart. This happens at a pressure higher than you would experience at the bottom of the deepest point in the ocean.

Ford Diesel Engine

Variable exhaust cam timing

The catalytic converter is an essential part of the exhaust system, which helps to filter the emissions and trap some of most damaging gases, but it only works above a certain temperature. Exhaust cam timing helps this system to warm up more quickly so the engine is cleaner for longer.

Diesel particulate filter

In this part of the engine the exhaust gas passes through a filter which traps particulate deposits so that they do not get released into the atmosphere. Once trapped in the filter, the deposits burn to ash and clear the filter, so it can keep catching particulate matter.

A diesel particulate filter (DPF) traps 99 percent of the soot in exhaust gas and this is a compulsory part of every Euro 6 diesel engine. The filter has ceramic and metal honeycomb plates which the gas passes through on its way out of the engine, and the soot is deposited on these plates.

Selective catalytic reduction

This is a specialist catalytic converter for diesel engines which uses a substance called AdBlue. The AdBlue is stored in a tank and is injected into the exhaust to convert nitrogen oxide into nitrogen and water, which are both harmless.

Lean nitrogen oxide catalyst

A lean nitrogen oxide catalyst is an alternative to the selective catalytic reduction. It works by storing the nitrogen oxide and then mixing it with exhaust gases to convert it into nitrogen and water.


This cools the air that comes out of the turbo charger, so that more air can be forced into the engine. This helps the engine to burn fuel more efficiently.

Exhaust gas recirculation

Controlling the engine temperature helps to reduce nitrogen oxide emissions. The exhaust gas recirculation system helps to keep the engine cool by recycling some of the exhaust gas back around the pipes.

Nitrogen oxide after-treatment

After this process, the exhaust gas is treated to reduce nitrogen oxide emissions. There are two types of after-treatment: selective catalytic reduction (SCR) and nitrogen oxide absorber catalysts (NAC). SCR injects a substance called AdBlue into the gas to convert nitrogen oxide into nitrogen, which is harmless, and NAC uses chemical absorption to remove nitrogen oxide from emissions.


The autocatalyst, or catalytic converter, contains precious metals and makes the exhaust gas cleaner by extracting the carbon monoxide gas and unburnt fuel particles.

If you would like more information on Euro 6 or diesel engines, contact your nearest Peoples Ford showroom and speak with a member of the team who will be able to help.