The furfural molecule has a very high oxygen content. In addition, its derivatives are known to change the phase diagram of (e.g. diesel), so that mineral diesel can be blended e.g. with alcohols without forming emulsions. Already in earlier work and field trials , such additives have successfully reduced diesel emissions or suppressed e.g. the vapour pressure so ethanol-gasoline mixtures did not separate! The attached patent falls into this category of chemistry. 

Extract from US Patent #8,372,165

A diesel fuel blending component primarily comprised of 1,2-(ditetrahydrofuryl)ethane (DTHFE) along with a method