Thursday, December 18, 2025

What’s DEF? | The Each day Drive

A bit of DEF cleans a number of air.

Fuel-pump side DEF dispenser.
Gasoline-pump aspect DEF dispenser.

Generally known as DEF, diesel exhaust fluid is an emissions after remedy, launched to the exhaust gasoline of a diesel engine to diminished nitrogen-oxide (NOx) emissions.

You could have seen DEF (also referred to as AdBlue, which is a model title) within the aisles of a truck cease or ironmongery shop. The fluid, which is comprised principally of urea and water, is usually bought in 1- and a pair of.5-gallon containers, in addition to bigger vessels to be used in over-the-road vans. DEF can be retailed at truck-stop gas pumps in bulk type, which is handy for truck operators, as massive tractor trailers usually have DEF tanks as giant as 20 gallons. Diesel-powered pickup vans have smaller DEF tanks, usually 5-6 gallons.

What’s DEF?

Emissions

Essential to the operation of what’s generally known as the Selective Catalytic Discount (SCR) system, DEF employed appropriately can assist to scale back NOx emissions by as a lot as 90 p.c. Probably the most harmful byproducts of diesel combustion, NOx emissions contribute to respiratory issues, acid rain, and ground-level ozone, also referred to as smog. Environmental Safety Company (EPA) laws mandating the usage of DEF have been handed into regulation in 2010, requiring that each one heavy-duty diesel engines constructed starting in 2015 make use of the SCR system.

DEF in 1-gallon jug.
DEF in 1-gallon jug.

DEF Packaging and Costs

The fluid itself, which is about two thirds water and one third artificial urea, will not be particularly costly, and might run from $8-$12 per gallon, relying on the retailer and package deal dimension. The pump-side dispensers are usually the least-expensive buy choice. A 20-gallon DEF tank will present a typical over-the-road truck with about 6000 miles of operation.

Limp Mannequin

By regulation, as soon as a car’s DEF speak is depleted, the truck in query will function in “limp” mode, which reduces engine energy output till fluid is added to the tank. A warning that the DEF tank is approaching empty usually seems on a truck’s instrument panel roughly 100 miles upfront of full depletion.

Tampering

Whereas it was briefly well-liked for the operators of diesel-powered vans to take away the SCR programs, that motion has confirmed detrimental to long-term possession of the car. Not solely is tampering with the SCR system unlawful, many dealerships will decline to take an clearly tampered-with truck in commerce.

Automobiles

Truck requiring DEF use embrace diesel-powered heady-duty variations of the Chevrolet Silverado, Ford F-Sequence pickup, GMC Sierra, and Ram pickup. These along with all diesel-powered medium- and heavy-duty vans.

Deal with with Care

Dried DEF tends to crystalize on car surfaces, so care ought to be exercised when including the fluid to your car. Left to dry, DEF could fade painted physique panels.

DEF SCR System
DEF SCR system.

Take heed to the Automotive Stuff Podcast

Observe Tom on Bluesky

Observe Tom on Twitter

DEF Photos

Click on beneath for enlarged photographs

What’s Winter-Mix Gasoline?

Client Information Automotive Stuff Podcast Episode 267: Cadillac Kills Sedans, Hyundai Tucson Hybrid, Finest Household Automobiles


Related Articles

LEAVE A REPLY

Please enter your comment!
Please enter your name here

Latest Articles