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Performing an oil and filter change on your car
Why is an oil and filter change so important for my car?
Every aspect of routine maintenance on your car is important, but few are more so than ensuring your engine oil is in good condition. As well as prolonging the life and reliability of the car, it will help to make sure it’s safe to drive.
Although there are many other maintenance jobs that need regular attention on your car, its engine deserves particular care. is at the very heart of what makes a car a car. It’s responsible for moving the car along the road and provides power for all the systems that make it comfortable and safe to travel in. Engine oil lubricates parts and prevents wear and damage to the engine. It can even help you save fuel.
While it's easy to keep your car in good general health. many people overlook the importance of oil changes. Read our guide to find out what your engine oil does and why changing it regularly is so vitally important. We'll even show you how to change it yourself.
What does engine oil do?
Your car’s engine oil has a multitude of jobs to do, depending on the model. The most important task the oil in any engine is responsible for, though, is lubrication.
Your engine contains hundreds of parts which move in different ways. Without lubrication most of these would gradually wear out as they make contact with each other. The force of one mechanical part rubbing against another is referred to as friction, and that’s something you really don’t want in an engine.
Friction is the enemy of mechanical efficiency, as well as being responsible for premature wear, excess heat, vibration and noise. An engine without any internal lubrication would be noisy and rough, would use far more fuel than it should and worse. wouldn’t run for very long before it broke.
If there is too much friction between two mechanical components they can lock together and cause the engine to stop running. This is referred to as seizure and often spells the end for an engine. A seized engine will usually require a complete strip-down for repair and this is often not economically viable.
What does an oil filter do?
As the oil is circulated around the engine it can sometimes pick up deposits. Sometimes the channels through which oil travels can contain microscopic contaminants, which could be tiny particles of metal from the engine left there from the manufacturing process. Wherever they came from, it’s the job of the oil to clean them out.
As oil picks up these deposits it becomes dirty, and this is where the oil filter comes in. As the oil is pumped around the engine it passes through the oil filter, which is designed to remove contaminants in the oil. The oil filter is designed to last for the same amount of time as the oil, so when the oil is due to be changed, an oil filter replacement should be performed, too.
Where is the oil in my engine kept?
Most engines have a trough at the bottom of the engine that its oil will pool in. This is referred to as either the ‘sump’ or the ‘oil pan’. Oil sits in the sump when the car is switched off. When you start the car, the oil pump sucks the oil from the sump and distributes it around the engine.
When the engine is switched off the oil will gather in the sump again, dripping and flowing down from the engine components under the force of gravity. The depth of the oil in a car’s sump can be measured using the ‘dipstick’ – though on some cars it’s also measured electronically by sensors.
Do I need to check my oil level?
It was once the case that you needed to check your oil level before setting off on pretty much every journey. Modern cars can go for months without the engine oil level changing, however, it’s still always a good thing to know that your oil level is correct.
The owner’s manual for your car should outline any routine checks that are recommended for your car and you should follow its recommendations where at all possible. To ensure the efficient and reliable running of your car, a monthly check of the oil level of your car is a quick and easy task that will give you reassurance.
You’ll find a description of how to check your oil level later in this article.
Why does my oil level go down?
It’s natural for an engine to ‘consume’ a certain amount of engine oil as part of its normal running. The amount of oil an engine will consume can vary. The oil level of a healthy engine is likely to drop slightly when brand new – every engine has a ‘running in’ period before which is behaves in its normal fashion.
The oil consumption of an engine is likely to increase again as it gets older. As the internal mechanical parts of an engine wear it may become possible for oil to enter the engine’s combustion chambers, where it will be burnt alongside the petrol.
It is possible for the engine to burn oil in tiny amounts for a long time without causing significant harm, but as the issue worsens it can cause damage to the car’s catalytic converter. It can also cause the vehicle’s exhaust emissions to reach a level too high to pass the MOT. Blue smoke from the exhaust is the most obvious indicator that your car is burning oil.
Oil may also be lost through leaks, so pay special attention to the amount of oil in your engine if you notice unexplained oily droplets, stains or pools beneath your car. An engine oil leak is not necessarily a disaster, but can indicate the existence of a more serious fault.
If you suspect that your engine is consuming too much oil, you should take your car to a garage to be checked by a mechanic.
How do I check my engine oil level?
Most car engines will have a dipstick to enable the engine oil level to be checked. Your car’s owner’s manual will confirm if it has one and where it is located. Otherwise it will outline the procedure you should follow if it uses an electronic oil level gauge.
You’ll need a piece of old cloth or some kitchen roll, and it’s a good idea to wear some disposable gloves. It’s also a good idea to wear old clothes, and keep long hair and loose jewellery away from engine components.
Your engine should be cold, or at least cool, before you check your oil. This is to ensure you don’t burn yourself on a hot engine and that the oil has been able to trickle back into the sump.
The engine oil dipstick is, on most modern cars, mounted near at the front of the engine. It may have a bright yellow, orange or red plastic handle, often marked with an icon resembling an oil-can (it can look more like a watering can). Once located, take a firm hold and carefully withdraw it from the tube it sits in. There will be a resistance and you may need to pull quite firmly. Make sure that you pay attention to where the dipstick came from so you can easily replace it.
The dipstick will be marked with two indicator lines which may be labelled MIN and MAX. The ideal is for the oil level to be halfway between these two marks. You’ll likely get a false reading the first time you withdraw the dipstick, so clean the oil off using a piece of scrap cloth. Make sure the dipstick is clean and then replace it in the guide tube, ensuring that you press it fully home.
Wait a few seconds and withdraw the dipstick again. This time the depth of the oil should be clearly visible on the dipstick and will, hopefully, fall between the MIN and MAX marks. If this is the case, you won’t need to do anything else, other than replace the dipstick and close the bonnet.
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If the oil level has been found to be at or below the MIN mark, it will need topping up. You can find out how to do this in the next section.
How do I change my engine oil and filter
Many modern cars will tell you when your oil needs changing, based on the time and mileage covered since the last oil change.
The oil change cost can vary hugely, so it’s worth shopping around and looking for oil change offers in your local paper.
However, changing a car’s engine oil and filter is a job which can be performed by any competent DIY mechanic without paying garage labour rates. If you have any doubts at all as to your confidence in performing this operation, we advise you refer your car to a qualified vehicle technician.
To perform an oil and filter change on your car you will need the following:
The correct quantity oil in the correct grade for your engine (details of this will be found in its owner’s manual)
The correct oil filter and and mounting washer if applicable. The correct filter can be found using an oil filter cross reference book at a motorist’s supplies outlet.
Replacement sump-plug washer if applicable
Oil-filter removal tool
Torque Wrench and record of sump-plug torque settings.
Suitable vessel or tray to collect waste oil - note this may need to hold up to ten litres of oil, depending on the engine size of your carl
You may also need an electrical inspection lamp which can be positioned in such a way as you can use it hands-free
We recommend wearing an overall or clothes that you’re not concerned about keeping clean, disposable rubber gloves and suitable eye protection when working under the car.
Draining your engine oil
You must have safe and clear access to the underside of your car, using workshop ramps, jack-stands or axle-supports. Never work under a car which is only supported on a jack.
The owner’s manual for your car will show points at which it can be supported safely on axle stands. To ensure your safety, we recommend that the raising and safe support of your car be overseen by a competent vehicle technician.
Once you have sufficient space in which to work under your car and it is securely chocked to prevent movement, you can begin the process of draining the engine. Opening and securing the bonnet is a good idea as it will let light through to help with vision beneath the car.
The correct sump-plug removal tool will take the form of either a key or a socket which can be attached to a wrench. If it is a key, it will engage with a square or hexagonal notch in the sump-plug, if it is a socket it will need to be placed over the plug and pushed fully home.
With an oil-collecting vessel in place below the sump and the tool engaged the sump plug can be unscrewed from its hole - usually anti-clockwise. This may require some force. It is recommended that force is applied as smoothly as possible as sudden shocks can risk damaging the sump of the car.
The sump-plug may start moving with a sudden jerk, so be careful that the removal tool remains firmly attached to the wrench as the tool releasing suddenly can cause injury or damage to the car.
As the sump plug unscrews further, engine oil will begin to surge out, so ensure you place vessel to catch the waste oil as spillages are difficult to clean up. With the sump plug fully removed, it’ll take a few minutes for the oil flow to reduce to a drip. Once this happens, you can start to remove the oil filter.
The oil filter is a cylinder a little larger than a tin can that screws onto the engine. It’ll usually have oil filter written on it, together with other information including a part code.
In some cases the oil filter will unscrew by hand, but it may be that you need to use an oil-filter removal tool – taking the form of either a chain or a metal strap – to securely grip the filter and unscrew it from its mounting. It will unscrew in an anticlockwise direction, and as it is unscrewed waste oil may begin to drip from it. Its removal may also cause waste oil to flow from the sump at an increased rate, so ensure that your waste oil collecting vessel is positioned in such a way as to collect oil from both locations.
Unscrew and remove the oil filter and pour out the oil inside into your waste oil collecting vessel. The replacement oil filter can then be fitted – it will screw into position in the reverse of how the old item was unscrewed and removed. The oil filter may have a washer that fits between it and its mounting. Ensure the old washer is removed if there is one, fitting the new one in its place.
Using your finger, apply a thin coating of fresh oil to the oil filter’s thread and the filter’s seal. Screw the new oil filter in place by hand, as firmly as you can without using excessive force. You must take care to ensure the thread if engaged, as crossing the thread could cause costly damage.
Your sump-plug can now be re-installed. If you have a replacement, which is strongly recommended, remove the old washer from the sump plug and fit a replacement. Use a small amount of fresh oil to lubricate the thread before carefully screwing the sump plug into its hole, ensuring that it goes in squarely, engaging properly with its thread.
You’ll need to be tightened the sump plug correctly according to the torque settings given by the manufacturer. While these are rarely listed in the owner’s manual, they can often be found on the internet or by asking a main-dealer workshop. It’s a good idea to have the correct workshop manual to hand as it’ll contain this, and other useful information for reference during your ownership of the car.
If the torque setting is 90NM, for example, set your torque wrench to that figure and gently tighten the sump-plug until the torque wrench clicks. The click indicates that the correct torque has been applied.
Remember waste oil must be properly disposed of. Your local civic amenity will usually handle waste oil and may offer oil filter recycling. Under no circumstances must waste oil be poured down the drain – this causes considerable environmental harm and can lead to substantial fines by environmental enforcement officers.
Re-filling your engine oil
With the waste oil drained, a new oil filter installed and the sump-plug correctly re-installed, You can now fill the engine oil to the correct level. Your owner’s manual will list the correct quantity of engine oil under its ‘fluids’ or ‘filling capacities’ section. When refilling your oil from empty you should always use a figure which states oil capacity including oil filter.
While some technicians use a measuring jug to ensure that the correct amount of oil is added, you can achieve the same result by buying oil supplied in containers that make up to the approximate oil capacity of your engine. For example, if your engine holds 5.5 litres of oil, a 4.5-litre and a 1-litre bottle will give the right amount of oil in total.
It’s important to never overfill the engine, though. The maximum level on the oil dipstick should never be exceeded as it can cause mechanical damage. That means it’s best to pour in a little oil and check the dipstick often.
Your engine will have an oil filler cap - often marked with OIL (note to avoid embarrassment, this can look like 710 upside down) or the same oil can that appears on the dipstick. Your owner’s manual will show you its location, you’ll find it towards the highest point of the engine. It will usually unscrew anti-clockwise.
Your fresh engine oil can be poured into hole once oil filler cap has been removed. You should pour the oil in slowly to avoid spillage and air bubbles. Oil being poured at the correct speed should be silent as it leaves the bottle. Gulps of air leaving the container usually mean that the oil is being poured too quickly.
Check the oil level using the same method as described earlier in this feature. It could be that the oil level is not yet high enough to register on the dipstick. Keep adding oil and checking the dipstick until the oil level reaches the halfway point between MIN and MAX.
You may find there is oil left over when the the correct level is reached. When the oil level reads as correct, re-fit the oil dipstick and the oil filler cap, check that the car is secure and out of gear and start the engine. Let it run for 30 seconds or so and then switch it off.
Check the oil level again. It will probably have dropped as the oil circulates through the engine and gathers in the oil filter. Add further oil until the correct level is reached on the dipstick.
With the oil level now correct, you have successfully changed the oil and oil filter in your car. Periodically check to ensure that there is no leakage of oil from the sump plug or the oil filter; tightening as necessary.
Is an oil change the same as a service?
Although the replacement of the oil and oil filter are a vital part of a regular service, they are far from all that is involved. A full service at a garage may also include air filter, fuel filter and spark plug replacement. It could also include a number of checks and inspections including tyre tread and brake pad thickness.
There are usually belt under the bonnet that can wear and need replacement, and if the car has a cambelt it too will need replacement at a particular age or mileage.
Servicing a car doesn’t include just only the engine. Bulbs may need replacing and adjustments may be required to items like handbrake cables. Depending on the service that your car is due, these items will either be included or chargeable if necessary.
If your garage mentions complicated-sounding components that you don't recognise, follow this link to our car mechanic jargon-buster .
What kind of oil does my car need?
Your owner’s manual will specify the correct viscosity for the oil in your car, given as an SAE value. Common types are named SAE10W40, 5W30 or 0W30.
As the next section outlines, there are other factors to consider when selecting an engine oil.
Is expensive oil better than cheap oil?
Expensive oil isn’t always better than cheap oil and a recognised brand name doesn’t necessarily tell the whole story. While a buyer has no way to determine the quality of oil inside a package on a shelf at a motorist’s parts and accessories supplier, they can at least determine its specification and suitability for a car.
Car manufacturers often issue a specification that ensures suitability for the car and will be listed in the owner’s manual.
There are other variations, too. Certain oils are formulated to offer better protection for older engines or for newer or higher-revving engines, and other oils are designed specifically for diesel car applications. There are also mineral and synthetic oils and those that are mixtures of the two.
Your supplier will be happy to make a recommendation, but paying more doesn’t necessarily mean that the oil will be better for your engine.
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