Engine oil plays a vital role in keeping an engine running properly, helping to lubricate moving parts, reduce friction and manage heat. The type and amount of oil required varies between vehicles, so it is important to check the specification recommended by the vehicle manufacturer for your particular make and model.
The Motor Ombudsman provides information for consumers and automotive businesses accredited to its Codes of Practice.
What engine oil does my car need?
The engine oil depends on factors including the vehicle manufacturer, model, engine, age and fuel type. Even two versions of the same model may require different oils if they use different engines.
Vehicle manufacturers normally specify a viscosity grade, such as 5W-30, together with any performance standards or approvals the oil needs to meet. Both should be checked when choosing oil, as products with the same viscosity grade may meet different specifications.
This means there is no single engine oil that can be recommended for an entire make or model range. The correct oil needs to match the particular engine, including both the viscosity grade and any manufacturer or performance specification given for the vehicle.
Why does engine oil need to be changed?
Engine oil needs changing as its properties can deteriorate with use, namely it breaks down from intense heat and pressure, and loses its ability to lubricate parts, cool the engine, and eradicate dirt. This is one reason manufacturers set servicing and oil-change intervals.
This therefore reinforces the importance of following the servicing and oil-change intervals recommended by vehicle manufacturers.
Understanding engine oil viscosity grade and specs
Engine oil comes with a particular engine oil viscosity grade, and it is important that the oil recommended by the vehicle manufacturer is used.
What does the engine oil viscosity grade mean?
Viscosity means how easily engine oil flows. Engine oil readily thickens as it cools and thins as it’s heated. The smaller the numbers on the grade, the easier it will pass through the engine.
An engine oil grade seen on the label of a bottle of oil, for example, is typically made up of three numbers and a letter. Using the example of 5W-40:
- ‘W’ stands for winter;
- ‘5’ indicates the cold weather (low temperature) viscosity (flow rate) of the oil; and
- ‘40’ denotes how thick the oil is under normal operating temperatures.
How to find the right engine oil for your car
To help choose the right engine oil, motorists generally need to identify three pieces of information: the viscosity grade, the required performance or manufacturer specification, and the amount of oil the engine holds.
Check your owner’s manual
The owner’s manual is usually the most reliable starting point. It should state the recommended viscosity grade and any manufacturer specifications the oil must meet.
For example, the manual may specify a grade such as 5W-20 or 5W-30 alongside a separate approval code. Matching the viscosity alone may therefore be insufficient if the oil does not also meet the required performance specification.
Some manufacturers approve several oils depending on the climate, engine or operating conditions, so it is important to follow the information provided for your particular vehicle.
Use your registration plate
Many oil manufacturers and automotive retailers provide online lookup tools that allow motorists to enter a vehicle registration number to identify compatible oils.
These tools can be helpful when narrowing down the options, although the recommendation should still be checked against the vehicle manufacturer’s requirements before buying.
Read the oil cap or dipstick
Some vehicles display the recommended oil grade, such as 0W-30 or 5W-30, on the oil filler cap or nearby in the engine bay. This can provide a quick reference when topping up, although the label may show the viscosity without the full manufacturer approval or performance specification.
What are the main types of engine oil?
There are different types of engine oil available for cars, and the main types are as follows:
Fully synthetic oil
Fully synthetic oil is engineered to provide consistent performance across a wide range of temperatures and is commonly specified for newer engines.
Semi-synthetic oil
Semi-synthetic oil combines synthetic and mineral base oils.
Mineral oil
Mineral oil is refined from crude oil and is more commonly associated with some older vehicles.
The appropriate option depends on the engine and the manufacturer’s requirements, so the oil type should be checked alongside the viscosity grade.
How much oil does my car need?
The amount of engine oil needed varies by engine size, and the figure for a full oil change is different from the amount normally needed for a top-up.
As an example, Ford lists an oil capacity of 4.6 litres, including the oil filter, for a car with a 1.0-litre EcoBoost engine. The same manufacturer also states that approximately one litre takes the oil level from minimum to maximum on the dipstick for that application.
For a full oil change, check the specified oil capacity and whether the quoted figure includes a replacement oil filter. When topping up, motorists should use the dipstick or electronic oil-level display rather than assuming that the engine needs its full stated capacity.
How to check your engine oil level
Checking the oil regularly can help identify when the level is becoming low.
Running an engine with too little oil or using an unsuitable specification may contribute to mechanical problems. When it is too low, a light will often come on whilst driving, and it is important at this point to pull over safely and turn off the engine right away to avoid any damage.
Wait for a short period before checking the oil level, and add more before driving the vehicle.
What you’ll need
For vehicles with a conventional dipstick, which can often be found as a yellow plastic loop sat within the engine cover on the top of the engine, you will usually need a clean cloth or paper towel to wipe the dipstick clean before checking the level. The vehicle should be parked on level ground. Follow the manufacturer’s instructions on whether the engine should be cold or allowed to stand for a specified period after running.
Some newer vehicles use an electronic oil-level display instead of a physical dipstick.
Step-by-step: reading the dipstick
Remove the dipstick and wipe it clean before inserting it fully again. Remove it once more and check where the oil sits between the minimum and maximum markings.
If the level is close to or below the minimum mark, oil may need to be added. Avoid filling above the maximum level, as too much oil can also cause problems.
How to top up your engine oil
Use the oil grade and specification recommended for the vehicle. Slowly add a small amount at a time through the oil filler opening, then allow it to settle before checking the level again.
Continue until the oil sits within the recommended range. If the vehicle is using oil unusually quickly or regularly requires topping up, it may be worth having the cause investigated by a qualified technician.
When to get a full oil change and where to find a garage
Oil should generally be changed according to the servicing schedule set by the vehicle manufacturer. The interval may be based on mileage, time or the vehicle’s own service indicator.
A full oil change may also be appropriate if the oil has become contaminated or if a garage identifies an issue during servicing or repair work.
Motorists looking for a vehicle repairer, such as a garage, can find one that is accredited to The Motor Ombudsman’s Service and Repair Code on The Motor Ombudsman’s Business Finder.