NOVELTY - Fuel composition for cold start conditions, comprises: a liquid fuel comprising alcohol fuel or diesel, where the liquid fuel has a flash point temperature higher than 25 degrees F; and nano-sized zinc oxide particles (0.01-100 ppm), where at least 90 wt.% of the nano-sized zinc oxide particles have a size of 1-50 nm.    USE - The fuel composition is useful: for combustion in cold start conditions; for increasing an engine speed and an exhaust gas temperature of an internal combustion engine; for lowering a flash point temperature of a liquid fuel (all claimed); in hydrocarbon fuels including alcohol fuel (methanol fuels and ethanol fuels), alcohol containing fuel (methanol-containing fuels and ethanol-containing fuels), and diesel (non-petroleum diesel e.g. biodiesel, biomass to liquid diesel and gas to liquid diesel, and petroleum diesel); in fuel-injected and non fuel-injected engines including two-stroke engines and four stroke engines, automobile engines (including motorcycle engines, jet engines, marine engines and truck/bus engines), internal combustion engine (including an Otto-cycle engine, a diesel engine, a rotary engine and a gas turbine engine), intermittent internal combustion engine, and a continuous internal combustion engine.    ADVANTAGE - The fuel composition: is safe and environmentally friendly, as it improves the combustion and does not contain hazardous metal or metal oxide; provides increased fuel performance when the engine is under load, by decreasing the sensitivity or difference between research octane number and motor octane number levels; has the nano-size particles, which remain suspended over a longer period of time compared to relatively larger particles; exhibits an increased engine speed and/or an exhaust gas temperature; and improves the cold startability by reducing sliding friction between pistons of the engine and the cylinder walls.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) increasing an engine speed and an exhaust gas temperature of an internal combustion engine, comprising: providing the internal combustion engine with a fuel composition comprising a liquid fuel comprising alcohol fuel or diesel, and nano-sized zinc oxide particles; and    (2) lowering a flash point temperature of a liquid fuel consisting of alcohol fuel or diesel, comprising: combining the liquid fuel with nano-sized zinc oxide particles (0.01-100 ppm), where at least 90 wt.% of the nano-sized zinc oxide particles have a size of 1-50 nm.