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Modified Vehicles

Aftermarket Car Engine Oil Additives

There are many oil additives on the market that claim to offer numerous performance-improving advantages over just using an oil as the manufacturer intended.

Generally speaking we are dubious about these kind of claims; we recommend using a high quality engine oil straight out the bottle rather than messing around with its formulation.

Engine oil additives for the purpose of an engine oil flush at service time are a different thing completely and are not the subject of this article.

Shop For Engine Oil Additives

Are "Performance Improving" Oil Additives Beneficial?

There are several oil additives that can be bought easily and claim to provide amazing benefits for your car or bike, such as increasing the fuel economy, restoring worn engines and gears, increasing engine life and quietening the engine and transmission. We don't advise the use of these products as a good oil should contain all of the necessary ingredients for a vehicle to run properly.

Chlorinated Paraffin Additives

These are very common additives that you will find in many automotive retailers.

  1. They all contain chlorinated paraffin ‘extreme pressure’(EP) compounds first used in the 1930s in heavily-loaded industrial gearboxes, and in some automotive transmission applications, mainly hypoid gears.
  2. They all corrode copper-based alloys at moderate temperatures, easily exceeded in all engine, and most transmission applications. This problem was recognised in the 1930s, and chlorinated compounds were never used in transmissions with bronze bearings or gears. No responsible manufacturer ever suggested using them in engines where their increasing activity at high temperatures could lead to piston ring corrosion and bore glazing. (For the same reason, modern ‘hypoid’ additives are not used in engines, even though they are much safer than any chlorinated additive.)
  3. Chlorinated paraffin additives were abandoned by responsible lubricant manufacturers for automotive transmission uses in the 1950s. Chlorinated compounds still find applications in metal working, but their use is on the decline because of health and safety considerations.
  4. When burnt, chlorinated paraffins produce corrosive hydrochloric acid, and organo-chlorine compounds including the highly poisonous phosgene gas. Apart from these corrosion and health hazards, with petrol engines the deactivation of exhaust catalysts is also a problem
  5. Unfortunately, these additives give spectacular results in simple EP test machines such as the "Falex". As a marketing ploy, a demonstration of this type looks impressive to those not acquainted with the above facts. Also attractive is the low cost of chlorinated compounds, allowing profits of several thousand percent to be made.

Other Additives

As well as the chlorinated paraffin additives there are other types of aftermarket additives available and they may also be sold as a mixture of different kinds of additives.

PTFE and "Friction Reducing Particles"

Many claim to contain metallic particles and PTFE that will cling to the insides of your engine to repair wear or reduce friction. That just isn't possible due to the friction coefficient between the 'magic' additive particles and the engine / transmission components being much less than needed for the particles to stick, and that is with dry components, when you add oil to the equation there is no chance of the particles adhering to the engine/transmission. All that happens is that the additive flows through the system, until it reaches the filter and blocks it. This kind of product has been tested and tested with all kinds of measuring equipment; none have found any evidence that the additives have done what they are supposed to have done.

Oil Thickeners

Another common type of additive is the oil thickener. They may be sold as products to reduce oil consumption, stop smoke or stop leaks, which they may well do, but by thickening the oil, they are reducing the lubrication of the engine. These products are extremely thick petroleum based oils that when mixed with engine oil, increase the average thickness of the oil in the engine to something far thicker than recommended for that engine. Cars are designed to run on certain oil grades and if one of the thickeners is used with what would be the right grade of oil, the oil will be far to thick to provide a good level of protection.


Good modern oils contain all of the necessary ingredients to keep your vehicle running properly and as long as the oil is changed in accordance with manufacturer guidelines, the oil will protect car more than adequately. The off-the-shelf additives available today are generally just a waste of money, but some are harmful too. Your vehicle will be much better off with you saving the money on additives and getting a decent oil.