Modern car oil is a real labour of lab...

QUESTION Engine oil is semi or fully synthetic. How is it made? MINERAL or conventional oil is refined crude oil. It doesn’t come with the engine-cleaning agents required for modern cars and can operate only within a limited temperature range. It’s recommended only for older cars.

Synthetic oil is made in the laboratory using various distillation and purification techniques. Though usually petroleum based, it is refined, distilled and broken down to its basic molecules.

Impurities are removed and the oil is tailored for optimal performance for specific engine types. Synthetic oil is engineered to provide optimal lubrication over a wide range of temperatures and operating conditions, while reducing drag on the engine to help reduce fuel consumption.

It is less prone to evaporation and has a high viscosity index, so it degrades less, resulting in less of the dreaded sludge, a tarry deposit that can damage engines. Detergent molecules actively clean the engine as it’s pumped around. This increased engineering means synthetic oils are expensive.

Semi-synthetic oil, a blend of mineral and synthetic oil, is a cheaper alternative. Dr Ken Warren,

Glasgow. QUESTION Why is crossdressing known as drag? ACCORDING to the Oxford English Dictionary, the word has existed since around 1388, though not until the 19th century was it used in connection with performing in clothes or a persona different from your own gender.

For hundreds of years, the idea of women acting was scandalous, so it was men who played female parts on stage, dressing in women’s clothes.

It’s believed that drag became a term to describe long skirts dragging along the stage floor. Actors would refer to putting on petticoats as putting on their drags. Emilie Lamplough, Trowbridge, Wilts.