Dilution of oils with solvents and microemulsions of plant
oils lowers the viscosity; some engine performance problems,
such as injector coking and more carbon deposits, still exist.
Among all these alternatives, the transesterification seems to
be the best choice, as the physical characteristics of fatty acid
esters (biodiesel) are very close to those of diesel fuel and the
process is relatively simple. Furthermore, the methyl or ethyl
esters of fatty acids can be burned directly in unmodified diesel
engines, with very low deposit formation.