DIESEL EXHAUST FLUID – DEF

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What Is DEF? All You Need To Know: 

DEF or diesel exhaust fluid is an aggregate used typically in diesel-propelled medium and heavy commercial vehicles to reduce harmful exhaust gas emissions. Diesel exhaust fluid is made from a mixture of urea and deionised water. Deionised water is purified water with all the ions removed through the process of deionisation. This formulated mixture is injected into the exhaust stream which integrates Selective Catalytic Reduction (SCR) systems.

Why Is DEF Used In Trucks? 

DEF which consists of a formulated mixture of 32.5 percent urea and 67.5 percent deionised water, became a requirement when BS6 engine norms were announced by the government. This became mandatory to reduce the harmful effects of diesel engines on the environment. Precisely, this was added to the regulations since diesel fluid emits nitrogen oxides and particulate matter, harmful to crops, affecting the food supply consumed and air quality.

What Does The BS6 Emission Rule State? 

With the BS6 rules and regulations made mandatory, automakers are now expected to manufacture trucks with proper testing of diesel powertrains. As per the rules, automakers must ensure that their diesel engines should reduce hydrocarbon and nitrogen oxide production by 43 percent with a strict requirement to reduce NOx levels by 68 percent and particulate matter by 82 percent.

How Often Should You Refill DEF?

The frequency of refilling the diesel exhaust fluid of trucks depends on different factors including the size of the DEF tank, efficiency of the powertrain, operating conditions and the type of haulage applications the vehicle is utilised for.

However, on average, the rate of DEF consumption in trucks is around 2-4 percent of diesel consumption. For instance, for every 350-400 litres of diesel consumed, the vehicle might take up 7-8 litres of DEF. But, these figures vary from truck to truck. Moreover, smaller commercial vehicles with diesel engines require DEF refill less frequently.

How To Know When To Refill DEF? 

Generally, a warning is offered on the instrument cluster of commercial vehicles, indicating that it is time to refill the DEF tank. It is usually indicated using a gauge, or symbol resembling a droplet. If a DEF lamp lights up on the dash, it means one of the following: