By weight, gasoline contains about or by volume , quoting the lower heating value. Gasoline blends differ, and therefore actual energy content varies according to the season and producer by up to 1.75% more or less than the average. On average, about 74 L (19.5 US gal; 16.3 imp gal) of gasoline are available from a barrel of crude oil (about 46% by volume), varying with the quality of the crude and the grade of the gasoline. The remainder is products ranging from tar to naphtha.