Lead Replacement Petrol
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Lead Replacement Petrol (LRP) is a fuel developed to provide an alternative to leaded petrol. Leaded four star petrol was withdrawn from sale in the UK 2000, eight years after the last cars using it were made, and LRP was introduced containing other metal salts (such as potassium or manganese), enabling the large numbers of cars still using the fuel to continue running.
Leaded petrol contained a substance known as tetraethyl lead or TEL, a compound of lead in liquid form originally added to petrol to increase its octane rating. A side effect of adding TEL is that a layer of lead compounds forms on the valve faces of the engine, retarding wear.
Lead is very toxic and lead compounds in exhaust gases escape into the atmosphere causing pollution. Impacts on human health are widely documented. This led to the introduction of lead-free petrol.
With normal lead-free petrol an adjustment to the engine's ignition timing solved pre-detonation problems (pinking or pinging) caused by the lower octane rating, but this did nothing to prevent accelerated valve wear. The use of lead in petrol had allowed the machining of valve seats directly in the cast iron or aluminium cylinder heads (or block of side-valve engines). Over time these seats would heat up, erode and even micro-weld the valve to the seat causing rapid damage.
Lead Replacement Petrol was introduced to address the issue of valve wear.
However, by August 2002, it was reported in the British national media that most petrol stations would soon be withdrawing Lead Replacement Petrol from sale, despite there still being some 1.5 million cars using it. The supply of the fuel has since dwindled away to practically none. Older cars frequently seen on Britain's roads at the time which used the fuel included the 1976-1983 Ford Fiesta, 1980-1986 Ford Escort, all but the newest Ford Sierras and most 1980s Austin Rover models.