Our cars and the way we drive them are changing. Advances in technology and the growth of diesel engines have made our cars more sophisticated, and the ever-increasing speed of life keeps us moving more than ever before. With the greater demand we place on our vehicles, the recommendations of engine manufacturers and OEMs become increasingly important. Despite longer service intervals, we should never forget to check the oil level in our cars.

This means that between visits to the garage, it's more important than ever to check the oil level regularly and top it up when necessary. Most car manufacturers recommend you check your oil every 1,600 km. This is because, as the oil level drops, the remaining oil in your engine has to work harder, becoming dirtier and wearing out faster - with the result that your car's performance may start to suffer.

Not much further down the road, your engine could be in real danger of increased wear, overheating and even total seizure. Some oils thicken or break down when temperatures are too hot or cold. Without adequate lubrication, friction can harm engine parts. To counter this, Mobil™ engineering has produced a range of remarkably stable lubricants that perform in high and low temperatures. When you next visit a Mobil Service Station, remember that regular oil top-ups help prevent engine wear and prolong your engine life.

Ideally, you should check your oil once a week as recommended by most car manufacturers. If the oil level drops from maximum to minimum after less than 1000 miles (1500 km), you should have your engine checked. Oil consumption is different from one car to another and from one driving style to another.

How to check and top up your oil

1. Park on a level surface, turn off the engine and wait for 3-4 minutes to allow the oil to settle.
2. Find the dipstick, pull it out, wipe and re-dip before taking your reading.
3. If it is less than maximum, check the fill guide to find out how much you need to add.
4. Remove the oil filler cap on top of your engine, add the right amount of oil and replace the oil filler cap after the oil top-up.
5. Wait 60 seconds to allow the oil to settle into your engine, and then re-dip to check the new level. Add more oil if necessary and replace the oil filler cap.

Find out more from our Why, When, How leaflet Or view the FAQs section

Engine oil breaks down over time. When it breaks down, it loses its effectiveness and can no longer properly protect your engine.

In addition to lubricating an engine's moving parts, engine oil is designed to carry combustion by-products away from the pistons and cylinders. It is designed to deal with the small amounts of water that form as the engine heats and cools, and to collect the dirt and dust that enter the engine through the air-intake system. It also handles acids that are formed by the reaction between water and other contaminants. Sometimes there are even fuel leaks (fuel dilution) or coolant leaks that get into the oil system.

As a car is driven, the level of contamination in the engine oil constantly increases. The oil filter removes particles as the oil passes through the filter, but over time, oil additives are used up and the oil itself can start to degrade (oxidise or thicken). At that point, the oil can no longer do its job and must be changed.

The rate at which contamination and additive depletion occurs depends on many variables. Driving conditions may vary greatly and have a direct effect on the useful life of the oil. Other factors include the precision of ignition, fuel injection or carburetion adjustments, air cleaner service and the general mechanical condition of the engine.

Oil should be changed before the contamination level reaches the point where engine damage can result. Because it is difficult for the individual motorist to determine when the contamination level is too high, automobile manufacturers provide recommended oil change intervals. These change recommendations vary by model year and manufacturer. Recommended intervals and mileage limits also vary with the type of service under which a car operates. More frequent oil changes are recommended for severe service.

Engineers work to establish an optimal viscosity for oil, based on load and speed conditions. They balance lighter – or low-viscosity – oil, which provides little resistance to motion thereby saving fuel and efficiently transferring horsepower, with a heavier – or high-viscosity – oil that resists being squeezed out of the contact area between metal surfaces.

The complicating factor is that the viscosity of oil varies with changes in temperature – thinner when hot, thicker when cold. At low temperatures, we need the engine oil to flow readily (not thicken too much or gel). At high temperatures, we need the engine oil to keep from becoming too thin and allowing metal-to-metal contact. To counter this, engineers developed multi-grade engine oils.

Viscosity is a measure of a fluid's resistance to flow. A fluid with low viscosity flows easily and is often called "thin". Water is an example of a fluid with a relatively low viscosity. A fluid with high viscosity is often described as "thick". Maple syrup is an example of a fluid with a relatively high viscosity.

If the cloud is relatively blue or blue/black, it may indicate that oil is being burned along with the fuel. A possible cause may be either worn piston rings or an oil viscosity that is too low.

If the cloud is black, it indicates that excess fuel is being burned.

If the cloud is white, it may simply be the moisture in the cold engine and exhaust system being burned off. If there's a lot of white smoke and it continues for a long time, you may have an internal coolant leak.

Engine oils are currently classified by a two-letter code. Gasoline engine oil categories start with the letter S (originally designated "Spark Ignition" engine oils, we now associate the S with "Service"). Diesel engine oil categories start with the letter C (originally designated "Compression Ignition" engine oils, we now associate the C with "Commercial").

The second letter is simply a sequential designation of improving quality levels over time. In other words, when a new industry quality level is established, the next letter of the alphabet is used (so SJ replaces SH). The letters "I" and "K" were purposefully skipped to eliminate potential confusion with other commonly used designations.

The viscosity index (VI) number is a measure of the relative change in viscosity of oil over a temperature range. The HIGHER the viscosity index, the SMALLER the viscosity change over temperature. The VI is not related to the actual viscosity or SAE viscosity, but is a measure of the rate of viscosity change.

The VI number is typically used only as an indicator. The actual performance results of low-temperature pumpability tests and high-temperature wear tests for engine oils are better predictors of good performance in an engine.

Generally, multigrade oils (0W-40, 10W-30, etc.) will have high viscosity indexes. Monograde oils (SAE 30, 40, etc.) will have lower viscosity indexes.

Your oil warning light can come on for a number of reasons including: low oil level, a failing oil pump, a faulty oil-pressure sensor, blockage in the oil system, and excessive foaming of the oil. In all cases, you should shut down your engine as quickly as it is safe to do so. Continuing to operate your engine with low oil pressure can result in serious engine damage.