AdBlue is designed to be used straight out of the bottle without any dilution. Due to the nature of the system, it could cause damage to your car if you do attempt to use diluted AdBlue. AdBlue must meet the requirements set out in ISO 22241-1 and be made up of 32.5% refined urea and 67.5% demineralised water - anything else is illegal to sell under the name AdBlue.