Mineral oil refining businesses process crude petroleum and other mineral oil feedstocks into usable fuels and industrial materials. Refining commonly involves separating the feedstock into fractions by heating and distillation, then treating or converting those fractions to meet product specifications. Processes can include removing sulphur and other impurities, blending components, and producing oils with particular characteristics. Products may include petrol, diesel, aviation fuel, heating oil, liquefied petroleum gas, fuel oils, bitumen, lubricating oil base stocks, waxes and petrochemical feedstocks. Some businesses also re-refine used lubricating oils, recovering base oils and separating contaminants for treatment or disposal. Work is carried out using large-scale plant, storage and quality-control systems, with processes and product ranges varying according to the feedstock and the refinery's equipment.