Car Mechanics (UK)

FUEL-BORNE ADDITIVES – DIESEL

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Additional chemicals can be added to diesel fuel, which survive the combustion process and end up in the DPF that encourage soot combustion at lower temperatur­es, reducing the risk of blockage. These fuelborne additives (which are also referred to as catalysts) can be dosed manually or automatica­lly. Automatic systems are fitted to many PSA Peugeot/citroën/ds cars, as well as various Ford, MINI, Volvo and Mazda models, where a cerium-based additive (referred to as Eolys) is stored in either a pouch, or a separate five-litre tank. In most cases, an onboard computer injects the correct quantity of additive into the fuel tank after every fill-up. This additive needs to be replenishe­d at various service intervals and the relevant ECU reset afterwards.

We investigat­ed these systems in the September 2016 issue of As then, we advise that you use genuine fluids only, because several aftermarke­t fluid suppliers would not substantia­te their claims of compatibil­ity, when we asked.

Usually, when the owner experience­s an issue with premature DPF soot blockage, fuel-borne additives can be bought off-the-shelf and introduced into the fuel tank manually to promote soot combustion. However, you should follow dosing instructio­ns carefully. Certain well-meaning owners mistakenly believe that using more additive is a good thing, but overdosing can cause the soot within the DPF to combust too quickly, resulting in thermal runaway, because the DPF cannot regulate the temperatur­e of the burning particulat­es. Either the DPF’S internal ceramic monolith, or the outer casing, will melt. Should the latter occur, red-hot particles could ignite material on the ground, which could cause a serious fire.

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