Engine oil additives are designed to help lubricate and allow your engine oil to flow safely and help protect vital components of a combustion engine. They come with all sorts of roles and can benefit your engine in many different ways.
Some additives help with the lubrication of the oil at hot and cold temperatures - both ends can have a drastic effect on engine wear. If oil isn't at its best optimum setting, you can risk bits of the engine wearing out faster, such as seals or O-rings.
Many synthetic engine oils use a load of additives that help make an engine flow more healthily. However, many mechanics won't use it and it's not always in the control of the owner to decide on which oil to use. Especially if you don't request anything specific when your car - or bike if you use 4-stroke engine oil - goes in for its annual service.
The best engine oil additives at a glance:
Editor's pick: STP Oil Treatment, 450ml - buy from Amazon
Best for protecting seals: Lucas Heavy Duty Oil Stabiliser - buy from Amazon
Best for both petrol and diesel engines: Wynn's Super Charge Oil Treatment - buy from Amazon
As a result, most cars will probably be running conventional oil in your vehicle's required grade - such as 5W-30 engine oil. And if you know yours does, oil additives can be a great way to expand the life of the engine. The level of choice can be complicated, so we've made things simpler by listing our favourites available across the net.
The best engine oil additives
Editor's pick
Via STPAvailable in either 300 or 450ml bottles, STP's Oil Treatment additive is designed to help lubricate engine oil effectively even when it's experiencing excessive heat and thins out.
Simultaneously, it helps reduce and clean up carbon deposits. If left untreated, you may be running higher emissions from your exhaust simply because of excess carbon throughout the engine.
Pros
- Effective in fighting against heat and carbon deposits
- Reduces oil consumption
Cons
- Petrol and diesel bottles are separate
The best oil additive for protecting seals
Via LucasDesigned to reduce engine component friction in cold and hard starts, Lucas Heavy Duty Oil Stabiliser encourages better lubrication and helps to seal minor leaks throughout your engine.
We don't recommend you rely on this product to solve major oil leaks. But it can be effective against minor seeps you might notice until you can get the correct seal or gasket changed.
Pros
- Great at maintaining an engine's health
- Helps with minor leaks
Cons
- Isn't as multi-purpose as others
The best synthetic oil additive
Via STPIf your engine's oil isn't fully synthetic, STP's synthetic oil treatment is a great way to prolong the life of your engine. Because, after all, you can at least add some synthetic treatment if you can't do all.
This product helps clear away carbon deposits in the combustion chamber and throughout your engine to help it run more smoothly - and ultimately a bit more cleanly. It also fights against engine gunk as well as oil oxidisation and the level of thickness in varying temperatures.
Pros
- Very effective at treating the side effects of conventional engine oil
- Useful if your engine isn't running synthetic oil
Cons
- Quantity isn't as great as STP's Oil Treatment
The best oil treatment for both petrol and diesel engines
Via Wynn'sThe main aim of Wynn's Super Charge Oil Treatment is to improve the viscosity (thickness) of the engine oil at high temperatures in order to improve lubrication.
It also helps prevent excessive exhaust emissions and oil consumption and protects the engine against oxidisation and wear. It's recommended for both petrol and diesel engines, which makes things easier as well.
Pros
- Very comprehensive for the price point
- Compatible with both petrol and diesel engines
Cons
- Quantity isn't as great as others
The best oil additive for reducing sludge and deposits
Via Wynn'sWynn's Formula Gold Oil Treatment is designed for use in a very wide application of engines and fuel types. It can be used in petrol, diesel, hybrid and even powertrains that run on LPG.
It helps reduce oxidisation, friction wear on vital engine components, and is a great additive for preventing engine sludge and carbon deposits.
Pros
- Great for reducing sludge and carbon deposits
- Compatible for all grades of engine oil
Cons
- Others represent better value for quantity
Things to remember with engine oil additives
Engine oil additives are brilliant at helping to lubricate the oil inside your engine. However, they cannot be seen as saints for engine health. Some additives will claim, for example, to stop and prevent leaks throughout your engine. But you should only take claims like this with a pinch of salt.
No additive can cure leaking oil if your cam cover gasket, O-rings, or other seals are perished. These additives should be viewed in the same way as fuel additives. Things like injector cleaners and fuel system additives clean up bits of the fuel system and allow your engine to run cleaner. But the difference isn't substantial. It's the same story with oil additives. The primary function is to help lubricate the oil at extreme temperature ends.
Of course, the last thing you should check is how compatible the product is. This implies whether the additive is compatible with petrol engines, diesel, or both. You don't need to use tools like Amazon Garage or others to check the compatibility since additives are designed with most oils in mind.
Aaron Hussain is a commercial content writer at Bauer Media writing for Parkers and CAR. He is obsessed with classic cars and anything with a fascinating story to tell.
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