cerium oxide, fuel consumption, catalysis, engine deposits
8nm cerium oxide is surface functionalised for diesel compatibility and added to fuel at a level of 5-8ppm. Static engine tests and large scale field trials show that engine fuel consumption is reduced by 5-8% and emissions, particularly of black carbon particulates and unburnt hydrocarbons are reduced by >15%. Cerium oxide acts as an oxygen donating catalyst which, as a refractory ceramic, survives the fuel burn and acts to improve engine performance in two ways. Firstly, the activation energy of cerium oxide is size related and as a consequence 8nm particles act to burn off carbon deposits within the engine cylinder at the wall temperature. The engine is progressively cleaned up by cerium oxide and performance improves. Secondly, the cerium oxide acts in the gas phase during the fuel burning to reduce the deposition of non-polar compounds on the cylinder wall. This indicates oxidation of fuel during the burn which in turn results in a reduction of engine deposit build up and carbon based emissions.