Reducing the exhaust emissions of unregulated pollutants from small gasoline engines with alkylate fuel and low-ash lube oil

We report exhaust emissions of regulated and unregulated gaseous compounds (aromatic, oxygenated, and nitrogen-containing compounds), particle mass and soot content for a series of 5 utility hand-held machines typically used in gardening and forestry operation in Europe. The engines were tested in the Vehicle Emissions Laboratory of the European Commission - Joint Research Centre. Two fuels, standard and alkylate fuel (trace content of aromatics), and 2 lubricant oils (semi-synthetic and low-ash) were used. With the standard fuel, we observed average emissions from 8 g/h up to 103 g/h of hydrocarbons and from 162 g/h up to 275 g/h of carbon monoxide (regulated compounds). A consistent fraction of aromatics was identified in the exhaust: 5-10 g/h of toluene and 1.7-3 g/h of benzene for the 2-stroke engines (below 0.6 g/h for the 4-strokers). The use of the alkylate fuel resulted beneficial in the reduction of several chemical species, in particular all the monitored aromatics (70-100% reduction) and the soot content of the emitted particles (27-90% reduction). These reductions can mitigate the adverse health effects of some toxic or carcinogenic compounds (e.g. toluene and benzene) especially for professional users with high exposure risk. The use of the low-ash lube oil had a lower impact than the fuel change and was engine- and compound-specific. The carbon monoxide emission limit reduction and the introduction of the alkylate fuel would be already feasible actions based on this study and existing scientific literature.