Diesel exhaust fluid, commonly called DEF, is used in diesel vehicles equipped with selective catalytic reduction systems. It is injected into the exhaust stream to help reduce nitrogen oxide emissions. DEF is not a fuel additive and should never be poured into the diesel fuel tank. For additional vehicle-maintenance products, browse Keller Heartt’s commercial truck supplies.

DEF should be kept in a clean, sealed container and protected from contamination, direct sunlight, and extreme temperatures. It should also be stored away from fuels, oils, dust, and other materials that could affect its purity. For more guidance on storage and handling concerns, review Keller Heartt’s DEF troubleshooting guide.

Yes. Contaminated DEF can cause warning lights, reduced engine performance, damage to the selective catalytic reduction system, or costly repairs. Water, fuel, oil, dirt, or the wrong dispensing equipment can all affect DEF quality. Keller Heartt’s DEF troubleshooting resource can help customers identify common storage, contamination, and system issues.

The right package size depends on fleet size, DEF usage, storage space, and how often new product can be delivered. Smaller fleets may prefer jugs or drums, while larger operations may benefit from totes or other bulk formats. For help planning DEF alongside oil, coolant, and other maintenance fluids, review the Keller Heartt fleet maintenance guide.

DEF should be dispensed with equipment specifically designed for DEF because standard fuel or oil pumps may introduce contamination or use incompatible materials. A 55-gallon drum typically requires a drum pump or electric dispensing system, while a tote usually requires an IBC-compatible pump and hose setup. Browse Keller Heartt’s BlueDEF products, pumps, and dispensing systems to compare available options.

For diesel fuel treatments, anti-gel products, and other cold-weather maintenance needs, visit the fuel and oil additives collection