Olive oil. Spanish olive oil is almost the only oil or fat used in Spanish cooking and is available in all supermarkets. Virgin olive oil is the juice extracted from the olives by simple pressing and contains the flavour, vitamins and nutrients of the original fruit. Virgin olive oil is graded according to its degree of acidity. The Extra has less than 1 per cent acidity and is considered by gourmets to be the finest. The distinct aroma and flavour of virgin olive oil means it is best used as a dressing rather than a cooking oil.