We’ve covered both diesel and petrol injector cleaners on Parkers, but you might be wondering what engine oil additives are. Essentially, they’re compounds that help improve the lubrication of your engine oil.
A whole range of additives are out there. From anti-oxidants which fight against corrosion and sludge to viscosity index modifiers, which stop oil from thinning out too much at higher temperatures. Oil additives come in all sorts of forms and many are combined to tackle a number of things.
One useful thing worth noting is that synthetic engine oils are made up using a load of these additives. This is why the performance and durability of synthetic oils is vastly improved over conventional base products.
The best engine oil additives at a glance:
Editor’s pick: STP Oil Treatment – Buy from Amazon
Best oil additive for preventing oxidisation: Wynn’s Super Charge Oil Treatment – Buy from Amazon
Best oil additive for protecting seals: Lucas Heavy Duty Oil Stabiliser – Buy from Amazon
Still, we understand that a lot of people will trust their local garages to service their cars and use whatever suitable oil is on site. This can mean that a load of cars aren’t using synthetic oil, so the room for adding in oil additives is quite large. Whether your car runs 5W-30 or 10W-40 engine oil, or many others, we’ve created a shortlist of the best ones you can buy to help your engine operate healthily.
The best oil additives
Editor's pick
It helps provide extra protection against excessive heat and reduces carbon deposits. This helps keep an engine running cleanly and smoothly while simultaneously reduces oil consumption.
Pros
- Provides layers of protection for your engine
- Helps reduce oil consumption
Cons
- Petrol and diesel bottles are separate
Best oil additive for preventing oxidisation
It's recommended for petrol and diesel engines and protects against high oil consumption but low oil pressure and compression.
Pros
- Helps add a layer of protection with older engines
- Combats oxidisation and ensures strong lubrication
Cons
- Isn't as effective as synthetic oils
Best oil additive for treating tappet noise
It's important to note that after adding, you should run your car's engine until it's at the warm operating temperature to bed in the additive.
Pros
- Helps prevent tappet noise
- Can be used in all petrol and diesel engines
Cons
- Quantity isn't great
Best oil additive for protecting seals
Rrp: $32.12
Rrp: $32.12
While this oil stabiliser is advertised to stop leaks anywhere from your engine to the differential, it won't stop an oil leak caused by a perished seal that desperately needs replacing. Think of it as a preventative measure that helps prolong your engine's life.
Pros
- Effective at maintaining an engine's health
- Quantity is generous
Cons
- Doesn't contain much other additives to help with other things
Best synthetic oil additive
The Synthetic Oil Treatment adds a layer of protection against engine wear. It focuses on carbon deposits in the pistons and helps the combustion process run more smoothly, preventing a build-up of unwanted gunk. It also helps reduce oil oxidisation (corrosion). It works with the oil's viscosity (thickness) at higher temperatures, again, a layer of protection to stop the oil from becoming too thin, which causes engine wear.
Pros
- Helps reduce oxidisation and carbon deposits
- Synthetics help add fluidity and protection
Cons
- Quantity isn't as generous as STP's regular Oil Treatment
Things to consider with oil additives
If my car runs synthetic oil, can I still use oil additives?
The simple answer is: it might not work very effectively. Fully synthetic oil is made of additives that help with the same things that sole oil additives are designed to do. Plus, synthetic oils have a habit of separating the sole additives rather than mixing the stuff in. You will have better luck if your car is running part-synthetic or fully conventional engine oils. Lots of high mileage engine oils use a load of additives, so it’s always best to check before you buy.
Do oil additives really stop leaks?
The purpose of some of these additives is to help reduce the thinness of engine oil at high temperatures. Thin, hot oil leaks out of seals more easily than when it’s colder and thicker, so they can help reduce or even stop leaks, depending on the overall conditions. Some additives even work in gearbox oils and even oils found in differentials. But these tend to be more specialist.
But our advice is that they’re not sealants to perished seals or O-rings, so if you do notice a leak coming from your engine or gearbox, it will probably need a very worn-out part replacing. The job of the additives is to act as preventative measures. But it can never replace the necessity of changing your engine oil.
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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