Oil Additives

Which oil additive do I need for my situation?

The right choice depends on your situation, not on a general preference for "something extra." Engine Flush cleans before an oil change. Engine Protectors and Worn Engine Treatments go into fresh oil afterward. Oil Leak Stop conditions aged seals to reduce minor seepage. Each type addresses a different problem, and using the wrong one for your situation adds little value.

If your symptom is a ticking noise from the top of the engine, a dedicated Hydraulic Lifter Cleaner is the appropriate product type. It dissolves varnish deposits in the lifter oil passages and is added to warm existing oil. Check the product range for the current options.

Using Engine Flush before an oil change and then adding an Engine Protector to the fresh oil is a safe and logical sequence. Do not add a flush to fresh oil, and do not run two additives with overlapping functions in the same fill.

Is an oil additive safe for your engine?

Oil additives work within your base oil. They support what the oil already does, but they cannot compensate for a wrong oil choice. If your engine requires a specific viscosity or specification, that remains the priority. An additive added to the wrong oil does not make the oil correct.

Compatibility notes by engine type and situation:

• DPF-equipped diesel engines: Oil additives that raise ash, phosphorus, or sulphur content can interfere with DPF function over time. Before adding anything to a modern diesel, confirm that the product label states compatibility with low-SAPS oils and DPF-equipped engines.
• Turbo engines: Most oil additives are compatible with turbocharged engines, provided the product is approved for the oil specification your engine requires. Check the label before use.
• Modern petrol engines (direct injection, GDI, TFSI, TSI): Compatible with suitable products. The same label-check applies, particularly for engines with a GPF (petrol particulate filter).
• Hybrid and start-stop engines: No specific exclusion for most oil additives, but the same compatibility rules apply. Confirm the product is approved for your oil grade and engine specification.
• Catalytic converters: Products that comply with ACEA C-series or equivalent low-SAPS specifications are generally safe. Avoid additives without a clear spec statement on the label.
• Warranty: If your car is still within the manufacturer warranty period and the OEM explicitly prohibits aftermarket oil additives, using one may give the manufacturer grounds to dispute a warranty claim. Check your owner's manual or contact your dealer first.
• Lease cars: Lease contracts vary. If your contract or the leasing company's maintenance terms restrict aftermarket additives, follow those terms. When in doubt, ask your fleet manager or dealer before adding anything.

If you are unsure which oil specification your engine requires, the Knowledge Center has guidance on oil grades and compatibility.

How and when do you use an oil additive?

One bottle per system is the standard rule for a typical passenger car. Dosage is calibrated for a standard passenger-car oil fill. Using more than the recommended amount does not improve results. It can shift the oil outside its intended viscosity or specification range, which is counterproductive. Do not mix additives with overlapping functions in the same oil fill unless the product explicitly states that is safe.

Use each product at the right stage:

• Engine Flush: Add to warm used oil before draining. Let the engine idle for 20 minutes, with no load or driving. Then drain the oil while still warm and replace the filter. Do not add Engine Flush to fresh oil.
• Engine Performance Treatment / Worn Engine Treatment: Add to fresh oil after the oil change, then drive normally to mix the product through the system.
• Oil Stop Leak: Add to existing oil. The effect builds gradually over several weeks and hundreds of kilometres as the seals condition. Monitor the leak during that period.
• Hydraulic Lifter Cleaner: Add to warm existing oil, then drive normally. The cleaning effect develops over hours to a few days of normal use.

Frequency by product type:

• Engine Flush: occasional use, not at every service. Use it when buying a used car, after an extended oil change interval, or when switching from unknown oil quality to a known specification.
• Engine Protectors: at each oil change for high-mileage engines, or every second oil change in normal use.
• Oil Stop Leak and Hydraulic Lifter Cleaner: typically a one-off treatment. Reassess at the next oil change.

What can an oil additive realistically fix, and what can it not fix?

Can help:

• Sludge and varnish from irregular or overdue oil changes (Engine Flush, before the oil change)
• Lifter ticking caused by deposits in oil passages (Hydraulic Lifter Cleaner; noise typically reduces over hours to a few days of normal driving)
• Minor seepage from aged but structurally intact elastomer seals such as crankshaft or camshaft seals (Oil Stop Leak; effect builds over several weeks and hundreds of kilometres)
• Gradual wear protection in high-mileage engines that are still mechanically sound (Engine Protectors and Worn Engine Treatment)
• Slightly quieter running in engines where noise is linked to lubrication quality rather than physical damage

Cannot fix:

• Worn bearings, scored cylinders, or broken piston rings
• Severe or fast oil leaks, cracked housings, or torn and hardened seals
• Persistent lifter ticking caused by mechanical wear or incorrect valve clearances
• Strong metallic knocking from the engine
• Low oil pressure
• Active fault codes or warning lights
• Heavy blue or white exhaust smoke
• Compression loss

The dividing line is straightforward: if the symptom is caused by deposits, aged seals, or a lack of protective film in an otherwise sound engine, an additive addresses the right problem. If the symptom is caused by physical damage, an additive does not. A garage inspection is the correct next step in those cases.

When should you go to a garage instead of using an oil additive?

An oil additive is a maintenance product for engines that are fundamentally sound. When the symptoms below are present, adding a product to the oil is not the right response. These signals point to mechanical damage or safety-critical faults that need diagnosis, not treatment.

Do not add any oil additive if:

• The oil pressure warning light is on
• You hear strong metallic knocking from the engine
• Heavy blue or white smoke is coming from the exhaust
• Your oil level drops noticeably between checks
• The engine has active fault codes or is running in limp mode
• The gearbox is slipping, grinding, or refusing to engage
• You notice steering play, heavy steering, or a sudden loss of power assist

If any of these apply, stop driving if it is safe to do so, and have the car inspected by a garage. A mechanic can identify the cause before you decide on any further steps.

For gearbox and power steering additives, see the relevant subcategories.

Is an oil additive worth it if your car already runs well?

If your car gets regular oil changes with the correct grade and specification, has no symptoms, and follows the manufacturer's service schedule, an oil additive is optional. The right oil, changed at the right interval, is still the primary protection for any engine.

The case for adding a protector is strongest with high-mileage engines, cars used under demanding conditions such as frequent towing or many cold starts in city traffic, and vehicles with an irregular or unknown service history. In those situations, the extra margin in the lubricating film is a reasonable choice alongside a correct oil change. For a well-maintained newer car without symptoms, there is no pressing reason to add one.

If you are unsure whether your situation calls for a flush, a protector, or simply a good oil change, the choice-helper table above is the quickest route to the right answer.