What is DEF?

Diesel Exhaust Fluid is produced to an international standard (ISO 22241). In order to meet the 2010 EPA Diesel Emission Standards to reduce the amount of NOx emitted by diesel engines, several engine manufactures employed Selective Catalytic Reduction (SCR) as an after-treatment technology combined with Exhaust Gas Recirculation (EGR). It is a specific composition of urea for application in transportation to reduce the amount of nitrogen oxides (NOx) emitted into the air by diesel engines. DEF is a high purity chemical, comprised of 32.5% urea and 67.5% de-ionized water.


How does DEF work?

As explained by the American Trucking Association (ATA), “To reduce NOx, a small amount of DEF is injected directly into the exhaust upstream of a catalyst. The DEF vaporizes and decomposes to form ammonia (NH3), which in conjunction with the SCR catalyst reacts with NOx to convert the pollutant into nitrogen (N2) and water (H2O).” 2.5 Gallons of DEF will yield over 800 miles of travel.

Consult your 2010 and newer vehicle owner manuals to determine if DEF additive is required. (NOTE: Some commercial vehicle engines have been modified making it unnecessary for additive).


DEF Availability

Coleman Oil Company offers DEF for pick-up or delivery in 330 gallon totes, 55 gallon drums or 2 ½ gallon jugs.  

We also offer the added convenience of being able to use your CFN card to purchase DEF.  See below for an interactive map of our convenient locations.


DEF at the Pump.  We offer four convenient locations for purchasing DEF with your CFN card.


North Lewiston Dyna Mart

1920 Highway 125/N&S Hwy

Lewiston, Idaho 83501



4520 Baldy Park Road

Sandpoint, Idaho 83864


Old Station (Wenatchee North)

2732 Euclid Avenue

Wenatchee, Washington, 98801



3160 E. Seltice Way

Post Falls, Idaho 83854


Tips for handling DEF this winter:


1. Know that it will freeze: DEF is a water-based solution, so just like water, it will freeze. Take precautions when using DEF in extreme winter conditions. DEF will begin as ‘slush’ before it freezes and will ultimately freeze into a solid state when the fluid temperature reaches 12 degrees F. However the process of freezing DEF has no effects on its quality or performance.

2. Leave room for expansion: DEF expands upon freezing by upward of 7%. Thus when storing equipment overnight or longer in temperatures that could result in DEF freezing, it is important to make sure that the DEF tank on the equipment is not completely full. This will allow for expansion and help prevent cracking of the storage reservoir. During winter, once the tractor is started, the DEF will thaw quickly and return to its usable state.

3. Store indoors: DEF packages and bulk storage should be kept indoors in temperature controlled environments.

4. Use the right container: DEF is mildly corrosive and should be stored in containers of HDPE plastic or stainless steel. Other metals may corrode when in contact with DEF and causes contamination.

5. Change the filter: The injectors that meter DEF into the exhaust stream are precision instruments with tight tolerances, similar to fuel injectors. Systems have a cartridge filter inside the pumping module to protect these injectors with a recommended 1,200-hr service interval.

6. Check the expiration: The storage life of DEF varies, its urea is vulnerable to degradation from sunlight and higher temperatures. In favorable storage conditions (proper container, away from direct sunlight, temperatures between 12 and 86 degrees F), DEF can maintain its qualities for about 12 months.

7. Handle it like fuel: Per EPA guidelines, vehicle using DEF must include sensors to analyze continually the quality of the DEF being consumed. These sensors will trigger a fault code whenever an imbalance is detected. Most commonly, this result from a higher percentage of water as a result of foreign matter, condensation or rainwater in the DEF storage container or during transfer.