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What happens if we put petrol in diesel (or vice versa)?

Model: (Various brands) Various
Part: Checks and maintenance

What happens if we mistakenly put the wrong fuel in our car's tank? If we put petrol in the diesel tank, it is a serious problem because petrol washes away the lubricating properties of diesel, causing the injectors to run 'dry', seizing within minutes. Additionally, in the high-pressure environment of a diesel engine, petrol can cause pre-ignition, risking damaging the pistons and causing severe engine and injection system damage. If you realise this, do not even insert the key, as the electric pump would activate, pushing the wrong fuel into the engine. Push the car to a safe place and call a mechanic to completely empty the tank. If, however, we put diesel in a petrol car, it is a less serious case: the engine often won't start at all because diesel does not ignite with the spark from the plugs, or it starts poorly and emits blue smoke. It can foul and damage the plugs, lambda sensor, and catalytic converter. If we put a small amount in a nearly empty tank, fill up with petrol immediately to dilute the diesel: the vehicle will run, albeit with some performance loss, until it has cleared the mixture. If we put a lot of diesel in, we need to call a mechanic to drain the tank.

Posted on 13 August 2026 by ScegliAuto

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