You Need to Know about DEF

06 Dec 2017, Posted by McPherson Oil in Industry Information

Fuel Services Diesel Gas | McPherson OilDiesel Exhaust Fluid, or DEF, is a critical liquid for a functioning, efficient, eco-friendly vehicle. It’s flushed through a Selective Catalytics Reduction (SCR) system, and it helps the environment by reducing the truck’s nitrogen oxide (NOx) emissions. 

Your drivers can easily stop at a fuel services station to purchase more DEF, but they shouldn’t wait until their truck is breaking down to make a stop. As a fleet manager, help them plan ahead by equipping your entire fleet with extra DEF. 

Here are some common questions about this very important fluid.  

What’s the History Behind DEF? 

As of 2010, any diesel vehicle sold in the U.S. must abide by the American EPA emissions rules. In an effort to reduce global warming, acid rain, and other harmful environmental toxins, vehicles must be equipped with technology to reduce NOx emissions. 

In response to this rule, diesel engine manufacturers have taken advantage of SCR technology, a concept that’s been around since the 1950s and used on commercial boilers. For today’s eco-friendly automobiles, SCRs use a catalyst, heat, and DEF to transform nitrogen oxides into nitrogen and water vapor. 

What’s DEF Made Of? 

DEF is made up of 32.5% high purity automotive grade urea and 67.5% water. Urea is nitrogen that, when heated, transforms in to ammonia.  

How Would a Fleet Benefit from Using SCR Systems? 

As the market’s stability ebbs and flows, your fleet’s budget has to remain a priority. SCR technology can support this effort since it improves fuel economy. SCRs filter out 90% of toxic fumes that would otherwise be circulated into a vehicle’s intake. Plus, since SCRs enable more NOx conversions, a truck’s engine is fully optimized, leading to better fuel efficiency.  

Can I Just Mix This Fluid Myself to Save Money? 

No. To meet EPA standards, each vehicle requires this specific formula of DEF. If you pour in the incorrect type or amount of fluid, the truck’s system will inform the driver of a contamination error. 

What’s DEF’s Shelf Life? 

As with most chemicals, extended exposure to heat and sunlight can tarnish its lifecycle. When it’s stored between 10-90 degrees Fahrenheit, DEF can last at least a year. If it’s stored at no higher than 75 degrees, its shelf life can reach two years. Its shelf life decreases to six months when it’s continuously exposed to 95-degree heat over time.  

Where Can I Buy DEF for my Fleet? 

Diesel Exhaust Fluid is available in Alabama, Georgia, Tennessee, and the Florida Panhandle through McPherson Oil’s distribution network. After four decades, we’ve become the largest private distributor of lubricants in the Southeast and have expanded with numerous partners. 

For your next DEF order, contact Customer Service at 1-888-802-7500 or email us at