This article provides a general guideline on prevention for misfuelling and DEF contamination in a Ryder vehicle. Misfuelling is a common but preventable risk for fleet operations. A momentary mistake at the fuel pump, often caused by similar-looking fuel caps, time pressure, or unfamiliar equipment, can result in severe vehicle damage, extended downtime, and significant cost. In modern fleets, where Diesel Exhaust Fluid (DEF) is widely used and multi-fuel environments are common, misfuelling incidents continue to occur. Understanding the risks, consequences, and prevention methods is critical to protecting fleet uptime.

Misfuelling Is a Fleet Risk

Misfuelling typically occurs when DEF is added to a diesel fuel tank and diesel fuel is added to a DEF tank. Contributing factors include the following:

• Similar-looking fuel caps and filling ports on some vehicles
• High driver turnover and varying experience levels
• Tight schedules and high-pressure fueling environments
• Fuel stations that support multiple fuel types (diesel, gasoline, DEF)

Without standardized fueling procedures and consistent driver training, fleets are more vulnerable to these errors.

What Happens When DEF Enters the Diesel Tank

DEF is a water-based solution and is not compatible with diesel fuel systems. If DEF is introduced into a diesel tank and the engine is started, it can cause severe damage, including corrosion of fuel system components and rapid crystallization that clogs fuel lines and filters; damage to high-pressure common rail systems; and injector blockage, leading to poor performance or engine failure

Once DEF circulates through the fuel system, repairs may require extensive component replacement and can lead to prolonged vehicle downtime.

What Happens When Diesel Enters the DEF Tank

• When diesel fuel is mistakenly added to the DEF tank, it contaminates the Selective Catalytic Reduction (SCR) system, which is responsible for reducing nitrogen oxide (NOx) emissions.
• Possible impacts include damage to the DEF pump, sensors, and fluid lines; clogging from sticky diesel residue; triggering of dashboard alerts and engine fault codes; and entry into reduced-power or derate mode.
• If the engine remains off, damage may be avoidable. However, once the system activates and contamination spreads, SCR components often require replacement.

The True Cost of Misfuelling

The impact of misfuelling goes well beyond repair costs.

Operational Impacts

• Missed or delayed deliveries.
• Disrupted routes and schedules.
• Vehicle downtime and loss of productivity.

Financial Impacts

• Costly repairs not typically covered under warranty.
• Towing and roadside assistance expenses.
• Rental or replacement equipment costs.
• Overtime labor to recover service levels.

Safety and Compliance Risks

• Drivers stranded roadside due to reduced-power mode.
• Increased exposure to traffic and weather hazards.
• Potential emissions compliance issues.

From a total cost of ownership perspective, misfuelling is a preventable event that can significantly distort fleet operating costs.

Best Practices to Prevent Misfuelling

Effective misfuelling prevention requires a layered approach. Encouraging reporting of near-misses also helps fleets address risks before damage occurs.

• Establish standard procedures such as creating standardized fueling SOPs, requiring mandatory fuel-type verification before pumping, and reinforcing “pause and confirm” practices at the pump.
• Train Drivers to include DEF and fuel-type awareness in onboarding, provide refresher training for existing drivers, and train drivers to recognize differences in nozzles, caps, and labels.
• Using visual safeguards like clearly labeling fuel and DEF tanks, using color-coded or uniquely shaped caps, and applying decals or visual reminders near fill points.
• Leveraging technology like fuel card restrictions, telematics alerts, fueling data monitoring, and analytics to identify risk patterns and repeat incidents.

If Misfuelling is Suspected or Confirmed

1. Do NOT start the vehicle
   • Starting the engine circulates contaminants and greatly increases damage.
2. Arrange for immediate system drain and flush
   • Removing the incorrect fluid as quickly as possible can reduce the severity of damage.
3. Report the incident promptly
   • Follow your organization’s incident reporting process and document vehicle information, fuel type involved, location, and circumstances. Proper documentation supports insurance, warranty discussions, and internal risk analysis.

Ryder Fleet Risk Services helps fleets reduce preventable downtime through a proactive, data-driven approach that includes driver training and awareness support. data visibility to identify risk trends and preventive maintenance alignment with fueling risks. For more information, contact FleetRiskServices@Ryder.com.

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