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Classic Engines, Modern Fuel

Comments on Topic: Petrol treatments/ additives

Submitted by Anonymous
24-Apr-2020

In the publication Classic Engines, Modern Fuel page 28 Chapter 3 ."Additives reduce the severity of oxidation , where oxygen combines with the molecules on the surface of the metals to create a metal oxide. This is most common when an acid comes into contact with a metal..."

On page 31 Chapter 3 entitled 'Ethanol blended petrol'...quote..." Unfortunately the additives sold to protect fuel systems against Ethanol give no benefit. While they will mix with the petrol, they will not mix with the ethanol/ water mixture..."

From what I have read and understand it is this ethanol/ water mixture that causes the formation of an acid which then attacks the metal surfaces.

My previous understanding was that the treatments / additives researched by the FBHVC addressed the issues of corrosion, is this not right..?

Submitted by The Author
24-Apr-2020

Unfortunately, the answer to your question is not simple. Are the treatments / additives effective? The answer is yes and no.

When dissolved in petrol, ethanol can "attack" metals in two ways. By oxidation and by galvanic corrosion. In both these cases the additives recommended by the FBHVC are effective. Simplistically, the additives consist of molecules that are like tadpoles with a head that attaches to the metal and a tail that repels the ethanol. This is how they stop the ethanol reaching the metal. These molecules are only active when dissolved in petrol.

When water gets into ethanol blended petrol, the ethanol is drawn out of the petrol into the water which becomes acidic. Unfortunately, the additive molecules are NOT soluble in water and remain in the petrol. As the acidic water drops to the bottom of the petrol tank or float chamber, it displaces the petrol, and the additive molecules. You then have an acid which is in direct contact with the metal - hence the corrosion. In this case the additives do not protect the metal.

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