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Q: Wrong antifreeze and fuel additive used and the car is noisy and runs roughly

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I need your advice on a serious issue with my friend's car. She said that her check engine light went on and the car ran roughly. There was a lot of noise of the engine too. When I checked the oil, it had a green color. My friend put in diesel engine antifreeze. She put a gallon of it. What's more, she thought that the car would run better if she put fuel additive. She put in a bottle of diesel engine fuel additive. What should she do with her car and how serious is to put antifreeze and additive for a diesel engine into Mercedes? Thank you in advance.

This vehicle should not be run any at all until it can be diagnosed and repaired.

In cases where coolant has been put into the engine, this can damage various engine components such as the bearings, pistons and crankshaft. The result may be serious engine damage, similar to what would happen if the head gasket were to fail. A qualified technician, such as one at YourMechanic, will be able to perform any service needs you may have. A good place to start would be a diagnostic inspection of the Check Engine Light.

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