Redex fuel system cleaners only contain the same additives found in premium fuel. The product has been tested at up to four times the suggested dosage level with no issues found. As a result, provided the product instructions have been followed, it is impossible for Redex to harm a vehicle.
The only way Redex could cause issues is if a full bottle was added to a quarter of a tank (or less) and then the vehicle would struggle to run as it’s deprived of fuel. If there are any issues with your vehicle, we advise you to seek the help of a professional mechanic.