The measurements with vegetable oil have revealed a linear
relation between viscosity and CO emissions. CO concentrations
were reduced by 28% when decreasing the viscosity from 9 to
3 cP. The same effect is observed in case of diesel combustion, with
a CO reduction of 21% when the viscosity was lowered from 3 to
1 cP. At viscosities above 9 cP the exhaust gas contained considerable
amounts of unburned fuel, presumably caused by incomplete
evaporation