Reasons why Ethanol/Petrol Blended Fuels are Not Recommended for use in Vehicles made before 1986

Introduction

This paper outlines the key reasons why vehicle manufacturers do not recommend the use of any ethanol/petrol blended fuels in vehicles made before 1986.

Ethanol has a number of important chemical and physical properties that need to be considered in a vehicle's design. Vehicles made before 1986 did not anticipate that ethanol would be blended with petrol and therefore were not designed for its use. These same vehicles are nearly twenty years old and the technology used has limitations when it comes to being able to compensate for the effects of ethanol. The materials in these vehicles have also been subjected to at least twenty years of wear and tear and are consequently more sensitive to the effects of using ethanol/petrol blended fuels.

Carburettor equipped Engines

Vehicles made before 1986 vehicles were predominantly equipped with carburettors and steel fuel tanks.

The use of ethanol blended petrol in engines impacts the air/fuel ratio because of the additional oxygen molecules within the ethanol's chemical structure. The oxygen content of ethanol is 34.7% which causes the engine to run lean. Being a mechanical device for supplying fuel to an engine, carburettors have a limited ability to compensate for this additional air. The consequences of which are the potential for pre-ignition, which will not only impact driveability but may also lead to engine damage.

Vehicles with carburettor fuel systems may experience hot fuel handling concerns. This is because the vapour pressure of fuel with ethanol will be greater (if the base fuel is not chemically adjusted) and probability of vapour lock or hot-start problems will be increased.

As a solvent, ethanol attacks both the metallic and rubber based fuels lines, and other fuel system components. Materials compatibility is a critical concern and unless the fuel system components have been selected on the basis of compatibility with ethanol, there is the serious risk of loss of function, resulting in the failure of plastic components in a fuel system.

Ethanol also has an affinity to water that can result in corrosion of fuel tanks and fuel lines. Rust resulting from this corrosion can ultimately block the fuel supply rendering the engine inoperable. Water in the fuel system can also result in the engine hesitating and running roughly.

Fuel Injected Engines

In addition to the issues mentioned above for carburettor equipped engines, the use of ethanol blended petrol in fuel injection systems will result in early deterioration of components such as injector seals, delivery pipes, fuel pump and regulator.

Mechanical fuel injection systems and earlier electronic systems may not be able to fully compensate for the lean-out effect of ethanol blended petrol, resulting in hesitation or flat-spots during acceleration.

Difficulty in starting and engine hesitation after cold start can also result.

Exhaust and Evaporative Emission Levels

Lean-out resulting from the oxygenating effect of ethanol in the fuel may affect exhaust emissions. Of more concern is that fuel containing ethanol can increase permeation emissions from fuel system components, particularly those that have aged for nearly 20 years. Therefore the increased vapour pressure of fuel with ethanol (if the base fuel is not chemically adjusted at the refining stage) will lead to increased evaporative emissions.