What Happens if AdBlue is Added to Diesel Tank

This is a critical situation. AdBlue is not a fuel additive; it is a water-based urea solution that is highly corrosive to your engine's internal components.

As a "misfuelled car fixer," here is the breakdown of exactly what is happening inside your vehicle and the rescue procedure required to save it.

If you haven't started it: Do not turn the ignition key to the "ON" position (which primes the fuel pump). Do not unlock the car if it wakes up the electronics. Keep the key out.

If you have started it: Turn it off immediately. Every second the engine runs, the AdBlue is being pumped into delicate, expensive components.

What Happens Inside the Tank (The Science)

AdBlue is roughly 67% deionized water and 33% urea. Diesel is an oil. They are chemically incompatible.

1. Separation: AdBlue is heavier than diesel. It sinks immediately to the bottom of the fuel tank—exactly where the fuel pump draws from.
2. Corrosion: AdBlue is highly corrosive to materials like aluminum, steel, and brass, which are used in fuel pumps and injectors. It strips the lubrication that diesel usually provides.
3. Crystallization: If the mixture enters the engine and heats up, the water evaporates, leaving behind hard urea crystals. These crystals act like sand, grinding down the high-pressure fuel pump and blocking the fine nozzles of the fuel injectors.

The Professional Rescue Procedure

If you call our professional misfuel rescue service (0330 122 6640), we will not just siphon the tank. AdBlue is sticky and crystallizes, so a simple drain is often insufficient.

Here is the standard professional fix:

Scenario A: You Did NOT Start the Engine

• Status: Good. The contamination is contained in the tank.

The Fix:

1. Suction Removal: The rescue technician inserts a probe into the fuel tank (often removing the sender unit under the rear seats to get to the very bottom).
2. Total Drain: They pump out every drop of the mixed fuel/AdBlue.
3. Flush: The tank is often flushed with clean diesel to ensure no AdBlue droplets remain stuck to the tank walls.
4. Refill: The tank is filled with fresh diesel.
5. Prime: The fuel system is primed to ensure no air locks.

Scenario B: You DID Start the Engine

• Status: Critical. The AdBlue has been pumped into the fuel lines, filter, and potentially the injectors.

The Fix:

1. Full Drain: The tank is drained completely.
2. Line Flush: The high-pressure fuel lines must be disconnected and flushed through with clean diesel to push out the AdBlue.
3. Filter Replacement: The fuel filter must be replaced. AdBlue will saturate the filter paper, and it cannot be cleaned.
4. Injector Inspection: If the car ran for a while, the injectors and high-pressure pump may need professional testing or replacement (this is where costs rise significantly).

Next Step for You

If you are currently stranded:

1. Do not try to dilute it by adding more diesel. It won't work; the AdBlue will still sit at the bottom.
2. Call our specialist fuel drain company immediately. (Search for "misfuelled car fixer").