With leaded petrol (super, 4 star etc) now a thing of the past, and Lead Replacement Petrol due to be phased out in Europe, there is still quite a demand for a Lead Replacement additive for all of the pre 1986 cars still on the road today.

Exhaust valves can reach temperatures of 850 Centigrade under normal operating conditions when using petrol, the petrol has a cooling effect when entering the combustion chamber. Besides increasing the octane quality, lead provides a critical wear reducing function by depositing a thin, protective layer of lead oxides on valves and valve seat surfaces reducing the risk of valve seat recession. Without a lead replacement additive, the valves will burn out at a rapid rate, leading to costly cylinder head repairs and possible major engine damage. The lack of valve lubrication often results in premature failure of exhaust valves due to a phenomenon known as valve seat recession.

The publication SAE-Australia, September-October 1993 states:

... One advantage of leaded fuel was that the lead helped to reduce exhaust valve-seat wear, especially in cast-iron headed engines not fitted with alloyed valve-seat inserts, but with valves running directly into the head. The use of unleaded fuel (or gas) in these engines is likely to cause rapid valve-seat recession and eventually burnt valves...
It further states:
... However, material used for valve-seat inserts for leaded fuels were not as good as the later insert materials, which are more resilient to wear. Such materials were developed specifically for unleaded fuel...

Flashlube Valve Saver Fluid with its lead substitute provides essential lubrication and protection to all pre-1986 engines, which required lead for lubrication. Since 1990 Flashlube, an Australian owned company, has sold Flashlube Valve Saver Fluid, a non-metallic lead substitute. This lead substitute had initially been used with great success in LPG converted engines providing essential lubrication to hot, dry valves and valve seats.

With Flashlube Valve Saver Fluid added to petrol the risk of valve and valve seat wear is greatly reduced. Because of pistons and ring wear many high compression engines do not have the original high compression any more and do run quite well on unleaded fuel. The cost to treat a tank of fuel is minimal considering the high cost of head repairs, replacement or illegal engine modification.

Detailed Problem Analysis
Because of a hotter engine, more engine oil is drawn past piston rings and through worn valve guides and/or valve seals. At high combustion temperatures the additives in engine oil will break down to ash and hard, abrasive oxides. The build up of deposits on valves and valve seats reduces normal valve cooling through the water cooled valve seats raising the temperature of the valves even further, creating additional problems:

Abrasive wear due to hard deposits between valve faces and valve seats. A small leak between exhaust valve and valve seat, caused by carbon deposit on the valve or valve seat will allow hot gases to escape. As the gases flow under extreme pressure through the small opening (blow-by), they will begin to erode the valve face. This blow-by will further increase the temperature of the valve head causing valve burning.
Excess carbon deposits on the valve stem will cause valve-sticking resulting in valve burning. At extreme temperatures, the hardness of the valves may not be adequate to prevent indentation of solid deposits (carbides) resulting in excessive valve seat wear and recession. The working stress of overheating valves and the absence of a lubricant to cushion the hammering effect between the hot, dry valves and the valve seats may cause the valves to deform and break. The broken valve head usually falls into the combustion chamber and in most cases will ruin the piston and cylinder walls.
Hot loose carbon deposits can trigger pre-ignition also known as deposit ignition. It may be audible or inaudible. Pre ignition causes the engine to compress burning gases. This pushes the combustion temperature well above the design criteria of valves and pistons causing rapid engine damage. At elevated temperatures oxidation of valve heads take place. This corrosive wear is due to hot gases, carbon dioxide, carbon monoxide, oxides of nitrogen, hydrocarbons, oxygen, water vapour, and several solid deposits causing pitting and wear. Also the high velocity of exhaust gas impinges on the valve stems and tends to erode the metal. Erosion and corrosion weakens the valve stems and leads to valve breakage. The corrosion rate increases with temperature.

How can you reduce the risk of premature cylinder head failure?
Use Flashlube Valve Saver Fluid, Europe's No.1 selling Lead Replacement Additive. With specially developed upper cylinder lubricants and cleaners most of the foregoing problems are reduced or eliminated. It cleans and controls valve seat deposits, resulting in better valve cooling through the valve seats and reduces exhaust valve overheating due to leakage of hot exhaust gases. The risk of valve sticking is reduced - also a major cause of valve and valve seat burning.

Flashlube Valve Saver Fluid is not an ordinary upper cylinder lubricant/cleaner. It is the first upper cylinder lubricant cleaner in Australia containing a lead substitute, greatly reducing valve seat recession and providing all the lubrication qualities of leaded petrol. Flashlube Valve Saver Fluid will increase the life of valves and valve seats and reduce component corrosion. The powerful cleaning additives control upper cylinder deposits, reducing the risk of pre ignition caused by hot combustion chamber deposits. The lubricant will maintain the performance and durability of your engine. It can be added directly to the petrol tank at a ratio of 1 to 1,000, or via the award winning Automatic Lubrication Kit. Thousands of kits have been installed in LPG and Petrol engines across Europe. Flashlube Valve Saver Fluid offers excellent protection when using unleaded fuel utilising the very latest oil industry technology.