What Engine Oil Does My Car Need?

All motorcars, whether boasting electric, or internal combustion, propulsion require lubrication to stop parts from rubbing together, overheating, wearing and failing.

While this blog provides a basic overview, be wary that modern cars are very fussy with their lubrication requirements and selecting the wrong oil can cause mechanical failure and is likely to void the warranty.

WHAT IS ENGINE OIL?

Motor oil comprises base oils, based usually on crude oil. These are combined by specialist chemical companies with additive packs to give the necessary performance characteristics needed to protect your engine, while maintaining optimum exhaust emissions and fuel economy.

WHAT DOES ENGINE OIL DO?

Engine oil lubricates and transfers heat energy away from highly stressed components. Most modern cars require synthetic oils, which are those blended with high-quality base oils. Additive pack compositions vary considerably. Engine oils for classic cars tend to have fewer detergents, whereas those for modern diesel engines possess complex cleaning chemicals within their formulations.

The latest engines also need special additives to protect their timing chains/wet belts, prevent low-speed pre-ignition and curtail intake coking. Extra additives also protect rubber seals, neutralise harmful acids and reduce the natural tendency for the oil to turn into sludge, as it oxidises. This explains why engine oil needs periodic changing at intervals that are specified by the car manufacturer.

WHAT IS THE DIFFERENCE BETWEEN SYNTHETIC AND SEMI-SYNTHETIC OILS

The difference between synthetic and semi-synthetic engine oil is a consideration that is not as relevant today as in the past. While the term 'Synthetic' might lead you to think that the base oil is not made from fossil fuel but some magical concoction, do not be fooled. Synthetic refers to higher quality base oil being used, the trend for which commenced around 25 years ago. Virtually all modern engine oils are synthetic.

Using a semi-synthetic oil in a car that specifies synthetic risks you using an oil that does not need the performance requirements that the engine manufacturer requires. The consequences may not be immediate but are likely to be higher levels of engine wear, increased exhaust emissions and, potentially, increased fuel consumption.

HOW TO FIND THE RIGHT OIL FOR YOUR CAR

When selecting engine oil for an older car, you need to consider the viscosity (expressed as 10w40 for example). Then, consider the general specifications that are provided by the API (the American Petroleum Institute) or the ACEA (European Automobile Manufacturers' Association) and match these to the car manufacturer's recommendations. Then, deduce whether the carmaker requires basic mineral oil, semi-synthetic, or synthetic.

Modern engines are far more exacting about their engine oil requirements. Therefore, car-makers provide a specification code. For example, if your car requires Ford 0W-20 WSS M2C 954-A1, you should use oil only that meets this requirement.

This information should be either in your handbook, or ask your main dealer. Alternatively, many oil blenders, or motor accessory stores, possess 'oil finders' databases, where inputting a registration number will match your car with the required motor oil.

HOW TO CHECK AND TOP-UP ENGINE OIL

Most cars possess manual dipsticks. These are metal, or plastic, calibrated rods, which are lowered into the engines' oil reservoir (sump), thus measuring the quantity of oil. The calibrated marks tend to indicate the safe minimum and maximum fluid levels.

With the car standing on level ground and the engine stationary, withdraw the dipstick and wipe the end with a clean, non-fluffy cloth. Insert the dipstick back into its tube, withdraw it and read the level (as pictured).

Some cars possess an electronic dipstick. Read your handbook for specific instructions on how it works, because some types are not very fast-acting, and you risk overfilling the engine with oil - which can be as damaging as not using enough.

HOW MUCH OIL DOES MY ENGINE NEED?

The general rule is not to allow the sump level to fall below the minimum, or maximum marks. Should your diesel car have a Diesel Particulate Filter problem, the oil level might rise. The reason is excessive quantities of diesel entering the sump. Should this occur on your car, have the DPF issue resolved and the oil/filter changed.

When conducting an oil change, your handbook should provide the sump's capacity - i.e. how much lubricant you need to add. Some oil finder databases provide this figure for you.

HOW OFTEN SHOULD YOU CHANGE YOUR OIL?

Your car manufacturer's service schedule will specify the oil change mileage and time intervals. It is essential to heed whichever interval occurs first. However, many technicians state that these intervals tend to be excessively long and recommend more regular oil changes. Much of this advice depends on how the car is used. For instance, frequent short trips tend to cause the oil to deteriorate faster than longer journeys. It is a good idea to ask your garage for more information. A general drain interval guide for owners that cover fewer than 10,000 miles in a modern car is annually.

ENGINE OIL AND THE MOT TEST

Engine oil condition is not assessed at the MOT Test, because the MOT is not a service. However, as elderly oil can result in worse exhaust emissions, poor maintenance might prevent the vehicle from passing indirectly. However, the tester may check the engine oil level. Should it be too low, the tester can refuse to continue the test, in case it damages the engine.

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