What should I do if I accidentally put AdBlue in my diesel fuel tank?

Created by Jonathan Fry, Modified on Mon, 19 May at 4:38 PM by Jonathan Fry

If you accidentally put AdBlue (a urea-based solution) into your diesel fuel tank, follow these steps to minimise damage and safely resolve the issue:

Do Not Start the Engine: Starting the engine can circulate AdBlue through the fuel system, causing damage to the fuel pump, injectors, and engine components. If the engine has already been started, turn it off immediately.
Assess the Situation: Determine how much AdBlue was added and whether it was mixed with diesel. A small amount (e.g., a few liters) may cause less damage than a full tank of AdBlue.
Do Not Drive the Vehicle: Driving can worsen the contamination and spread AdBlue through the fuel system.
Contact a Professional: Call a mechanic, roadside assistance, or your vehicle’s service center for advice. Inform them that AdBlue was mistakenly added to the diesel tank. They may recommend towing the vehicle to a garage to avoid further damage.
Drain the Fuel Tank: The tank will need to be drained completely to remove the AdBlue and any contaminated diesel. This should be done by a professional, as AdBlue is corrosive to certain fuel system components and requires proper handling.
Flush the Fuel System: After draining, the fuel lines, pump, and injectors may need to be flushed to remove any residual AdBlue. In severe cases, components like the fuel pump or injectors may need replacement if damaged.
Refill with Diesel: Once the tank and fuel system are cleaned, refill the tank with the correct diesel fuel.
Check for Damage: Have a mechanic inspect the vehicle to ensure no long-term damage occurred. They may run diagnostics to confirm the fuel system and engine are functioning properly.
Prevent Future Mistakes: AdBlue nozzles are typically smaller than diesel nozzles, but mistakes can happen. Double-check labels at fuel stations, and consider using clearly marked containers if refilling AdBlue separately.

Additional Notes:

Urgency: Act quickly to prevent AdBlue from sitting in the tank, as it can corrode components over time.
Costs: Draining and flushing the system may cost £100–£500, depending on the vehicle and labour rates. If components are damaged, costs could be higher (e.g., £1,000+ for a new fuel pump or injectors).
Warranty/Insurance: Check if your vehicle warranty or insurance covers misfueling. Some policies include coverage for such mistakes.

If you’re unsure or unable to contact a professional immediately, avoid using the vehicle and seek assistance as soon as possible to prevent costly repairs.