The Korea LPG Association has reported that sales of cars using liquefied petroleum gas have risen by a fifth in the first five months of this year.At the same time sales of petrol cars dropped 15 per cent on-year to 286,922 units, while those running on a liquefied mixture of propane, butane and other chemicals, reached 76,209 units, up from 63,303 an year earlier, reports the Korea Herald.