A1. All oil companies produce both cheap and expensive oils, none of them produce bad oil, you simply get what you pay for. Often the only differences are the price and service level. If a customer uses a specific supplier then a specific product can be recommended from that supplier's product range. We cannot comment on oil formulations or blending as this is the domain of the oil companies

A2. No, engine manufacturers in Europe, Japan and the USA design engines for specific purposes. They are all high powered and they all need different types of lubricants.

A3. Yes. However, because of their high cost, the benefits of using them should be balanced against the expense, taking into account the cost of the lubricated component, the application and the working environment. Synthetic oils generally protect components from high temperature operation but cannot protect them against contamination like dirt and water.

A4. No, just as engines and technology have advanced over the years, oil research and development have also progressed. Oil formulations can differ depending on the type and amount of additives used and the way in which the base oil was refined.

A5. Previously, synthetic oil was defined as an oil base stock that was formulated in a laboratory rather than crude oil from the ground that has been refined. However, these days the term 'synthetic' is purely a marketing term that denotes an oil of very high quality. Synthetic base stocks can either be synthesized in a laboratory or produced from very highly refined and processed mineral oils. Both 'mineral' and 'synthetic' oils contain additives.

A6. This is the same as asking why you should use fresh water and detergent when washing a new load of dishes. Like water, the base oil part of a lubricating oil does not wear out, but it also contains additives that help clean up contaminants, prevent rust, reduce friction, minimise foaming and so on. In fact, diesel engine oils also contain detergents and dispersants that clean the internal engine surfaces, neutralise acids and keep contaminants (such as carbon particles or soot) in suspension so that they don't form deposits on the mechanical components. In doing their jobs, additives are used up, and need to be replaced. So, just as you would change the dishwashing water in order to renew the detergent and remove the dirt and scraps that have accumulated, you also need to change the engine oil.

A7. The oil should be changed before the additives are used up. The vehicle manufacturer will provide guidelines for changing oil, based on either mileage or time period, in the operating manual of the vehicle. A bakkie, for example, might have a 12 month/15000 km oil-change interval.

A8. No. Black oil is a good sign that the oil is cleaning away the black deposits and contaminants that can form during the combustion process and get down into the engine oil. If the oil is still relatively light in colour when you change it, this means that it has little detergency and is not doing its job.