Is there a difference between a DPF additive and DEF?
Diane, Edinburgh, UK
The short answer is – yes!
DPF additives are often added straight into the vehicle’s diesel fuel tank. Some vehicles have a separate tank for a DPF additive which needs topping up occasionally to work with a specific DPF system. They contain chemicals called Fuel Borne Catalysts (FBCs) which are carried through the combustion process and into the exhaust system. Once there, they enter into the Diesel Particulate Filter (DPF) and help to burn away the soot which is collected and which can sometimes lead to problems with DPF blockage. You can find out more about FBCs on this page: FBC Chemistry
Diesel Exhaust Fluid (DEF, also known by trade names such as ‘AdBlue’ (a trademark of the VDA)) should definitely not be added to the fuel tank. DEF is a specially made solution of urea in water which is held in a separate tank on board the vehicle. It is released directly into the exhaust system (post-combustion) and works with a Selective Catalytic Reduction (SCR) system to lower the NOx emissions in the exhaust. You can read more about this and other technologies to reduce diesel emissions here: Other Technologies