Ethanol's effects on acid neutralization by motor oils

Sulfuric-acid neutralization by motor oils in the presence of ethanol was investigated for the first time by quantitatively visualizing the fate of acid drops in five off-the-shelf commercial motor oils via capillary video-microscopy. For all the oils at room temperature, there was neutralization when ethanol was absent, whereas little neutralization was exhibited when ethanol was present. A very different behavior was exhibited at 100 °C, with rate of acid neutralization being much faster in the presence of ethanol than in absence. With 1% ethanol and temperature of 100 °C, acid droplets were neutralized in 2 min, whereas at room temperature droplets expanded ∼35% in diameter after 60 min with little neutralization. The reported phenomena may affect engine behavior and tribology.