Motorists warned of ‘engine-knock’ when LRP is phased out in January 2011

Leaded petrol was banned in the EU around a decade ago due to air-quality standards and health issues. Instead, Lead Replacement Petrol (LRP) is used by some consumers who own an older vehicle originally designed to run on leaded petrol.

Newer EU fuel quality directives which will come into force on 1January 2011 will affect the current composition of LRP fuel by reducing the metallic to a third of what is currently present in LRP.

This means a reduction in metallic manganese additives that will affect the performance of LRP by reducing the octane number and the exhaust valve seat protection.

“A reduction in octane number might induce engine-knock, and the simplest remedy for such an issue might be to have the spark-timing retarded and adjusted accordingly by a professional mechanic,” an Enemalta spokesperson said.

“If this is not enough an ‘octane booster’, bought over the counter from the petrol stations, would have to be added to the unleaded petrol.

“The valve seat protection issue can be tackled in different ways. The simplest and cheapest solution is to purchase unleaded Petrol and add a suitable fuel additive that protects the exhaust valve seat from excessive wear.”

Another solution is to replace the existing exhaust valve seat to a hardened one, although this option is more costly but might be worthwhile if the engine is being reconditioned or the cylinder head is being removed for other mechanical maintenance or the car is kept as a classic.

Enemalta Corporation recommended that owners of vehicles that run on LRP seek the advice of a professional motor technician/mechanic to check if their vehicle is suitable to run on unleaded petrol. If not, they will be advised on what modifications and/or adjustments might be necessary to make such a changeover.