Diesel Exhaust Fluid (DEF) for Heavy Duty Trucks and Equipment

Modern diesel engines require Diesel Exhaust Fluid (DEF) to meet emissions standards and run efficiently. At Custom Truck One Source, we offer high purity DEF that protects your selective catalytic reduction (SCR) system, prevents derates and keeps your fleet EPA compliant.

What DEF Does for Your Vehicle

DEF is a non-toxic solution made of 32.5% urea and 67.5% deionized water. When injected into the exhaust stream it reacts with nitrogen oxides (NOx) to convert harmful emissions into nitrogen and water vapor. This simple process keeps your trucks running cleaner, more efficient and within federal emissions guidelines.

Why Quality Matters

Using low grade or contaminated DEF can damage your SCR system, clog injectors or cause premature catalyst failure. Poor quality fluids can trigger warning lights, power loss or put your vehicle in reduced performance mode. That’s why Custom Truck One Source only offers DEF that meets ISO 22241 and API Certified standards for purity, concentration and performance.

For Fleet & Vocational Applications

Our DEF products are available in multiple formats – from portable jugs for field refills to bulk drums and totes for shop or yard use. Whether you’re managing long haul rigs, utility fleets or off road equipment our solutions are formulated to perform in high load, high mileage applications. Each batch is produced and handled under strict quality control to ensure maximum shelf life and system protection.

Maintenance & Best Practices

For best performance store DEF in a cool, shaded area away from direct sunlight. Use clean dedicated equipment to prevent contamination and never mix DEF with other fluids. Replace aged or degraded fluid promptly and follow OEM recommendations for refill intervals. Proper DEF management maintains emission compliance, prevents injector clogging and avoids downtime.

Why Choose Custom Truck One Source

We understand the needs of heavy duty truck operators, service fleets and equipment owners. Our team delivers:

• Reliable high purity DEF that protects emission systems.
• Nationwide inventory and fast delivery options.
• Expert parts specialists who can guide you on storage, handling and system maintenance.
• One stop access to all the chemicals, lubricants and filters you need for your truck or equipment.

Stay Compliant and Running Strong

Get DEF for your trucks from Custom Truck One Source. Choose from below or contact our parts department. Tell us your vehicle make, model and system type and we’ll help you pick the right DEF and delivery for you.