These days, the world is filled with chemicals. They come in virtually every form imaginable, and life as it’s now known just wouldn’t be the same without them. Though they’re necessary elements, they can also do a certain amount of damage if left to their own devices. For this reason, an endless lineup of rules and regulations have been put into play for using them and dealing with their byproducts. When it comes to diesel engines, this is where DEF enters the picture.

What is DEF?

Short for diesel exhaust fluid, DEF is a compound used in vehicles and machinery that operate off diesel fuel. This additive has become increasingly well known over the past decade and is now a requirement for a number of businesses relying on such engines. It’s made of deionized water and urea. The former is simply basic H2O with all its excess electrons removed whereas the latter is a component of urine.

What Does It Do?

By nature, diesel engines generate nitrous oxide during their fuel-burning processes. This is a common pollutant released into the air via diesel exhaust. Once DEF is added to the mix, it serves to neutralize those harmful emissions by breaking them down into water and nitrogen. Both are then passed along through an engine’s exhaust system and dissipate harmlessly into the atmosphere.

How is DEF Used?

DEF use is a simple process. It’s poured into its own tank rather than the fuel tank itself and then passed along into the exhaust system. From there, it serves its purpose via a process known as selective catalytic reduction. All this is done automatically by an electronic control unit. Though DEF tanks don’t need to be refilled as often as fuel tanks, levels of this substance do need to be replenished from time to time.

Diesel engines are among the most efficient and effective fuel-burning options available for vehicles, heavy machinery and other types of equipment. That being said, they do generate their fair share of pollution. DEF was designed to help counteract this issue. Over the years, this substance has become a requirement, and it’s likely to grow more vital as emissions regulations become more stringent.