I will be in eternally grateful Saqib Sb. @spectra for alerting me to OAT (Organic Acid Technology) based coolants.
After some research I have found out that in 1996 the auto industry phased out IAT (Inorganic Acid Technology) based coolants and progressively replaced it with OAT coolants. The advantage of the OAT coolants is that they are long life, typically 5 years while the older IAT coolants have a 2- 3 year life. The reason for the shorter life is that the IAT coolant uses Phosphates and Silicates for corrosion protection. These chemical form a protective layer over the inner engine components and over time leech out of the coolant in providing the protection.
That is fine but the problem is that older cars like mine have a brass/copper radiator. OAT coolants attack not only brass and copper but also silicones used in sealing compounds, older rubber hoses etc. RROC (Rolls Royce Owners Club) and other older car clubs advise owners against the use of OAT coolants in their cars. So basically the normally available LLC (long Life Coolants) are not suited to pre 1995 cars. Cars that accept OAT coolants will have aluminium core radiators. IAT coolants are not to be used in these post 1995 cars because the corrosion inhibitors used in IAT coolants attack the aluminium of the radiator and cause the resulting flaking to choke the radiator.
So, in a nut shell, IAT coolants for pre 1995 cars and OAT for post 1995 cars. Of course this is general rule you need to check your own car's manual and make sure which coolant you need to use.
There are a number article to this fact on the web. Here is just one of them: Modern Automotive Coolants : How-To Library : The MG Experience
One other thing I have found out is that by-and-large the green coolant is IAT while the other colours are OAT. So now the hunt begins for IAT coolants.
