EU4, EU5 and EU6 refer to an engine’s European Emissions Standard. And by this we mean the emissions level a car or van must meet when it’s new. Obviously, the higher the EU rating, the cleaner the engine. When we apply this to diesels things get a little more complicated, because older diesels emit more harmful particles and gases than a petrol. In the future, diesels that don’t meet Euro6 emission standards will be restricted, banned or charged to enter cities in the UK. For more information, see: vans.honestjohn.co.uk/features/what-is-the-ultra-l.../