AdBlue
AdBlue is a key ingredient in certain Audi diesel models’ system that helps reduce nitrogen oxide emissions and just like the oil in your engine, it must be kept at the right level. If you need it, you’ll have an AdBlue filler cap under your diesel filler flap (or in the boot on older models). Your Audi will warn you when you’re within 1,500 miles of needing to top up your AdBlue, and it’s vital that this is done – either by you or your Audi Centre – to ensure your engine keeps working as normal.