How Can Winter Affect DEF? | McPherson Oil

20 Dec 2017, Posted by McPherson Oil in News

fuel services tank | McPherson OilWinter’s bitter temperatures can cause various problems for your fleet, like your fuel freezing and fluids thickening. When these road bumps arise, they can cause your drivers to miss their routes or have mechanics working overtime.  

Though your drivers can find diesel exhaust fluid (DEF) at their local fuel services station, it’s up to you as the fleet manager to ensure their trucks are fully stocked. Your trucks can’t run without it!  Not to mention that it can improve your fuel economy and advertising that you’re a green brand to increase your sales. 

With benefits like this, why would you not be using DEF for your trucks? Here’s the low-down on this very important fluid. 

What is DEF and Why Do I Need It? 

Diesel exhaust fluids (DEF) is flushed through a vehicle’s system called Selective Catalytic Reduction (SCR). It’s sprayed into the exhaust system, helping break down dangerous nitrogen oxide (NOx) emissions into water and nitrogen.   

These emissions contribute to environmental threats like global warming, acid rain, and damaging particles that can cause visual impairment. DEF is designed to be kept completely separate from all other oils and lubricants to reduce the emissions on the exhaust system. 

Using DEF in your trucks brings two major benefits to your company. First, it improves your fleet’s fuel economy by reducing exhaust gas by re-circulating the mixing water and urea. This stops about 90% of the harmful fumes from entering back into your truck. Second, businesses can increase sales by offering this eco-friendly or “green” solution.  

How Do Temperatures Affect DEF?  

Fortunately, as DEF freezes, it does not affect the vehicle operation. SCR systems provide heat to the DEF tank and lines during vehicle operation. No matter the temperature outside, the SCR system thaws the DEF tank to keep it flowing.  

Diesel exhaust fluid is 32.5% urea and 67.5% de-ionized water. When the engine is not in use or storage, it will not freeze until the DEF is at or below 12°F. At this concentration level, you will never have more urea or water than the other since they thaw at the same rate. This ensures that you always have the same amount of each fluid. If you have excess or not enough of one of the chemicals, the fluid will not function properly.  

When turning off a truck, a driver should wait 60 seconds before powering off the battery. This pause lets the fluids drain out of the hoses and into the DEF tank. If there’s no delay in the engine shutting off, the DEF solution thaws faster than it should. As a result, in inclement, freezing weather, the liquid expands inside the SCR.  

Learn how we can streamline your fleet and save you money for your Diesel Exhaust Fluid and SCR systems. Don’t forget to call McPherson Oil for Diesel Exhaust Fluid. Ask how we can lower your fleet spending at 1-888-802-7500 or email us at 

About: McPherson Oil is proud to distribute ExxonMobil products in the southeast including Alabama, Arkansas, Florida Panhandle, Georgia, Louisiana, Mississippi and Tennessee.