Are Engine Additives Worth the Try?

Are Engine Additives Worth the Try?


 – What is an engine additive?

 – Performance of engine additives

 – What are the conditions of the use of engine additives?

 – Price of engine additives

Engine additives are so-called preventive or curative products. They promise wonders, but manufacturers do not recommend them. What is their real efficiency?

What is an engine additive?

Engine additives include all preventive or curative products for the powertrain. There are several types of engine additives, all of which have targeted actions:

 – engine oil additives: they add extra molecules to the engine oil to eliminate impurities, increase oil change intervals, optimize the mechanical properties of the oil (shear strength, thermal resistance, etc.), restore engine compression;

 – engine feed additives: administered via the fuel tank, the air intake or by a specific injection station, they aim to improve combustion, remove water from the fuel, or clean the injectors, intake pipes and combustion chambers by removing carbon deposits;

 – cooling system additives: they act mainly in a preventive and sometimes curative way on possible leaks in the system (radiator, cylinder head gasket), they rid the system of impurities, scale and contribute to the anti-superheating;

 – gearbox additives: these products are added to the gearbox oil to alleviate gear shifting difficulties, reduce noise, “regenerate” the gearbox oil and plug leaks.

Engine Additive Performance

It is difficult to praise or condemn these products globally. However, it is possible, by studying each family of additives, to evaluate their effectiveness.

Engine oil additives

These products could be of interest given the increasingly long oil change intervals recommended by manufacturers (up to 40,000 km), but their effectiveness is highly controversial.

Despite the tremendous progress made by oil companies, it is illusory to think that oil retains its qualities for so long. Alternating heating and cooling of the engine lead to condensation in the engine, which oxidizes the oil. In addition, HDI engines pollute the oil with diesel fuel during the regeneration of particle filters. In the long run, combined with the deposits produced by combustion and the effects of the EGR valve, the oil crystallizes into a tarry liquid and loses all its qualities. In this case, additives, similar in composition to modern synthetic lubricants, could help.

Unfortunately, their cost is prohibitive and their action somewhat random, so it is preferable to choose regular oil change intervals.

Type of product

Examples of prices

Engine additive (famous brand) 400 ml


5 L can of synthetic oil Premium brand 5w30


Nevertheless, some engine oil additives have advantages; this is the case of additives for hydraulic tappets. By improving the oil’s viscosity, they eliminate noise caused by the failure of one of them. Given the cost of replacing one of these elements (removal of the camshaft and timing system), the use of an additive is an advantageous alternative.

It is essential to know that the administration of an engine oil additive by a professional is safe, primarily through the use of an injection station, which is effective. In addition, in case of a dispute, the responsibility will fall on the professional.

Cooling system additives

These products are effective in the event of a cooling system leak, especially for sealing a radiator. It is essential to know that these additives are only used for short-term repairs and that you will still have to replace the parts concerned.

Gearbox additives

A gearbox is made up of mechanical elements that are in friction. It is essential to know that a cracking noise when shifting gears is a sign of wear on soft metal synchronizer rings (generally brass-based). A continuous rumbling noise when driving is often the result of deterioration of a gearbox bearing (metal tearing off on the seats). In these cases, the use of an additive is entirely unjustified; the mechanical wear of these parts can only increase and lead to the destruction of the gearbox.

Moreover, financially, as for the engine oil, if we compare the additive and the gearbox oil (with the same characteristics), we can see that it is more advantageous to opt for frequent oil changes – although some manufacturers recommend lifetime use…

What are the conditions of the use of engine additives?

If, in the majority of cases, the use of this type of product will not have any consequences and will not damage your engine, it is helpful to know that:

 – any use of an additive will result in the nullity of the warranty during expertise following an engine breakage (often before a warranty coverage, an oil analysis, very revealing, is carried out);

 – If an additive is used, it is preferable to consult the manufacturer (car dealership) to find out if there is a commercial agreement (do not rely on the recommendations of the company producing the additive).

All service manuals advise against the use of fluids or additives that are not recommended. Here are two examples from car’s logbooks: 

– “Use fluids that meet the defined specifications or requirements. The use of other fluids may result in damage that is not covered by your vehicle’s warranty”; 

– “Items not covered: damage resulting from the use of fluids, parts or accessories other than original or equivalent quality, as well as the use of unsuitable or poor quality fuels and the use of any additional additives not recommended by the car manufacturer. “

Engine additive prices

Here are a few examples of prices.

Types of products

Price per litre

Motor oil additive

From $80 to $540

Engine Fuel Additive

From $75 to $150

In-station descaling treatment (performed by a professional)


Cooling additive

From $15 to $40

Gearbox additive

From $135 to $460

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