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Following is a question by the Hon. David Chu and an oral reply by the Secretary for the Environment and Food, Mrs Lily Yam, in the Legislative Council today(Wednesday).

Question:

Will the Government inform this Council:

(a) whether it knows the "octane numbers" of the petrol recommended by manufacturers for various types of private cars commonly used in Hong Kong;

(b) of the criteria adopted and factors considered in setting the "research octane number" at not less than 95.0 in the existing legislation in respect of unleaded petrol being sold in Hong Kong; and

(c) whether it has assessed how the level of pollutants concentration in vehicle emission will be affected if the petrol used by vehicles has an octane number higher or lower than that recommended by vehicle manufacturers?

Reply :

Madam President,

(a) The octane number of petrol reflects its ability to resist "engine knock", which in turn is the rattling of engine that results from premature ignition of the petrol. The higher the octane number, the more resistant it is to "engine knock". Based on information provided by vehicle suppliers, the manufacturers of about 95% of European made and close to 70% of Japanese made petrol vehicle models commonly used in Hong Kong recommend that these vehicles operate on petrol with an octane number not lower than 95. On this basis, we estimate that the manufacturers of more than 70% of petrol vehicles operating in Hong Kong recommend the use of petrol with an octane number not lower than 95.

(b) The minimum octane number in unleaded petrol was set in 1991 when unleaded petrol was introduced. In setting the requirement, we took due regard of the fact that vehicles operating on petrol with an octane number lower than that recommended by their manufacturers would emit a higher level of pollutants; while there would not be any effect on a vehicle's emission levels if it uses petrol with an octane number higher than that recommended by its manufacturer. In addition, we consulted motor vehicle suppliers and the oil trade. It was agreed that we should adopt the standard for unleaded petrol, including the minimum octane number, that would meet our environmental objectives and the requirement of the majority of the petrol vehicle fleet. We therefore adopted the European Union's requirement for unleaded petrol with an octane number not lower than 95.

(c) A vehicle using petrol with an octane number lower than that recommended by its manufacturer may consume more fuel, lose engine performance and risk "engine knock". The emission of pollutants such as hydrocarbons, carbon monoxide and carbon dioxide would also be higher because of reduced fuel efficiency and non-optimal engine operation. The actual level of increase would depend on the design, the age and the condition of the vehicles.

There will not be any effect on a vehicle's emission levels if it uses petrol with an octane number higher than that recommended by its manufacturer.

End/Wednesday March 1, 2000

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