For decades much more attention has been devoted to emissions from transport vehicles and to usage of various fuels and fuel blends for vehicle engine operation, than to fuel consumption by this giving a chance for under-researched aftermarket products that allegedly reduce engine fuel consumption. The paper summarizes four fuel innovation product investigations commissioned to and carried out by Department of Automotive Engineering of Riga Technical University in a year scope. The innovative solutions offered by entrepreneurs contained a fossil diesel fuel treated by specific technology and three diesel fuel additives. The promoters of the products referred to pre-existing measurements showing 10 to 30 percent reduction of fuel consumption. Comparative experimental measurements using diesel fuel available in retail with and without usage of the proposed products have been done in laboratory conditions. The tests were performed on stationary diesel generator RD2.0. Solid, repetitive results have been gained. The results did not confirm any significant positive effect of the products on engine brake specific fuel consumption. Factors affecting errors in this kind of product efficiency investigations for market promotion purposes and causes of positive effects from similar products applications in certain situations are discussed