When all’s well that oils well

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, so it’s recommended for older cars.

Synthetic oil is made in a 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 with specific engine types.

Synthetic oil is engineered to provide optimal lubrication over a range of temperatures and operating conditions, while reducing drag on the engine to help reduce fuel consumption.

it is not as prone to evaporation and has a high viscosity index. Therefore 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 runs.

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 was a gun once fired daily at 1pm in Liverpool? When did this practice end?

Further to the history of the one o’clock gun, fired so mariners could set their chronometers and discontinued in 1969, my mother always said you needed to have been born within the sound of the gun to be a true Scouser.

i could never figure out how this equated with the citizens of Birkenhead and Wallasey, who are affectionately known as oneeyed Scousers.

Phil Johnstone, Moreton, Wirral.