This is all completely new to me (and probably most folks unless they&#x27;re running around in brand new diesel vehicles). The last diesel car I owned was a 1998 (Euro-2 standard when NOx emissions were more relaxed - so no DEF required [0]) Ford Mondeo which I disposed of in 2006 when the timing belt snapped ruining the engine. Since then I&#x27;ve owned older petrol engined high mileage &quot;bangers&quot; so I would never have encountered DEF unless I won the lottery and fancied a new Landrover :)<p>[0]: <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;European_emission_standards#Emission_standards_for_passenger_cars" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;European_emission_standards#Em...</a>