Testing of Vegetable Oils in Diesel Engines

Abstract

In small engines, the fuel spray may impinge on cylinder walls, washing away the lubricating oil film, causing dilution of the crankcase oil with fuel, which contributes to excessive wear. Low viscosities may lead to poor penetration into the combustion chamber and poor performance. Vegetable oils are water-insoluble substances of plant origin which consist predominantly of glyceryl esters of fatty acids, so-called triglycerides. A vegetable oil that has a high degree of polyunsaturation would tend to oxidize and polymerize sooner in the crankcase of an engine than a vegetable oil which was highly saturated. Differences in physical and chemical properties of vegetable oils, compared to diesel fuel, should be given some consideration before evaluating the use of vegetable oils as fuels for compression ignition engines. The viscosity of the lubricating oil in the research test engine fueled by peanut oil increased abnormally during the normal 250 hours on an oil change indicating crankcase oil dilution.