All liquids tend to vaporize at atmospheric temperatures, but their rates of vaporization vary.
The rate of vaporiza-tion increases as the temperature increases and as the pressure decreases. In general, for a given temperature, a highly volatile fuel will vaporize more readily and at a faster rate than a fuel with a lower volatility. The volatility of fuel affects engine starting, length of warmup period, fuel distribution, and engine performance. High volatility, however, can also result in fuel dilution of the lube oil in the crankcase. The ways in which volatility can affect engine operation are discussed in the sections that follow.