How to change engine oil

Despite being one of the dirtiest maintenance tasks that you can perform, changing a car's engine oil is one of the most important. Despite their sophistication, modern engines suffer if their oil changes are neglected. As wear rates and even fuel consumption increases, neglecting oil changes to save money is a false economy. For some engines, degraded oil can even promote timing belt failure.

What oil does my car need?

Modern engines are very fussy about their oils. Filling up with the incorrect oil can cause considerable damage. Therefore, never pick a cheaper oil to save money. Older engines tend to rely on viscosity specifications (for instance 10W40), and/or API, or ACEA specifications. Modern engines have even more bespoke needs, so look for the manufacturer's specifications in your handbook. Typical examples of this are Vauxhall OV 040 1547-D30 or BMW Longlife-04.

If you cannot find your service manual's recommendations, there are multiple oil checkers online, operated by various engine oil blenders. These allow you to verify which oil is needed, by entering your registration number.

You will also need an oil filter. You can either visit your main dealer's parts counter, or your local motor factor. Avoid inexpensive, unbranded, white-box items from online marketplaces.

Should I buy oil additives?

It is worth buying an oil flush to dose into the sump of a warmed engine before draining the oil out. This helps loosen and remove contamination that reduces engine efficiency. It can even restore compression.

There is also a plethora of additives that you can add to fresh oil. Some of these aim to solve problems, such as swelling worn oil seals to reduce oil consumption. Others claim to fortify the oil and make it last longer. Should you decide to use them, do not overfill the sump.

How do I change my car's oil at home?

Once you have bought the correct quality and specification of oil, take your car on a short drive of 1-2 miles. This warms the oil, so it is easier to drain. Park the car on a level surface. Follow the instructions on your oil flush additive and run the engine for the prescribed period. Afterwards, switch off the engine, lift out and wipe the dipstick with a clean non-fluffy rag and remove the oil filler cap. If working outside, ensure no contaminations from the wind can enter the engine - working on a still day is ideal

You can buy bespoke oil drain pans. Place one under the car sump. It is a good idea to place newspaper on the floor but ensure that wind cannot whip it up, which could create a mess, while the oil drains out. Most cars are equipped with large plastic guards (undertrays), so work out how to remove them, so you can access the drain plug.

Unscrew the oil drain plug carefully, being wary that oil can flow out quite quickly, so be prepared. Wear protective gloves for this operation. Used oil is not good for your skin and could be hot. Wipe the removed plug and renew its crush washer.

As the oil drains, renew the oil filter; two main types of which exist. The metal canister type unscrews anti-clockwise. A new one is screwed hand-tight into place, after oiling its sealing ring. Many filters come with oiling and tightening instructions. Most modern cars use canister filters, where you unscrew a plastic cap, lift out the old paper element and replace it. You also have to renew any rubber sealing washers.

Again, many filters are supplied with basic instructions. Should your car possess a plastic canister, consider that overtightening can crack them. Use a torque wrench to tighten them to the specified value.

After you have installed the new filter, refit the sump drain plug. If not tightened sufficiently, the plug can work loose and cause a major oil leak, which could seize the engine. If you overtighten the plug, you risk damaging the sump's threads, which cause the same catastrophic result. Use your torque wrench to be safe.

Add fresh oil to the sump through the oil filler. Never add more than the amount stated in your car' capacity specifications. If your engine has a physical dipstick, do not exceed the maximum mark either. Refit the oil cap and start the engine. After ensuring that the oil light extinguishes, allow it to run for several minutes. Switch off the ignition and check for oil leaks. Recheck the oil level on the dipstick and top-up the oil, if necessary, but do not overfill it.

Refit the undertrays and record the oil change date and mileage in your car's service history. The waste oil should never be poured down the drain. Take it to your nearest household recycling centre for disposal.

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