Hi Wazza99,
Anti-freeze performs three functions in an engine; 
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1. Cold weather protection<o:p></o:p>
2. Overheating protection<o:p></o:p>
3. Corrosion protection<o:p></o:p>
Anti-freeze can be used at varying strengths to provide protection against the varying winter temperatures that we the users can expect. The stronger the antifreeze mixture, the colder the protection we get. 50/50 is a good mixture ratio for the UK and will protect your engine down to minus 35 degrees centigrade and boil over protection up to 129 degrees Celsius. However don’t use neat antifreeze in your system. No antifreeze should be used at strengths greater than 70/30.<o:p></o:p>
Aluminium is especially vulnerable to corrosion and many vehicles have heads, radiators and other aluminium components in the cooling system. If the coolant in an engine cooling system is changed before corrosion inhibitors reach dangerously low levels, corrosion damage is prevented.<o:p></o:p>
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The varying colours used by antifreeze suppliers denote;<o:p></o:p>
Green:<o:p></o:p>
Green antifreeze contains silicates, phosphates and borates as corrosion inhibitors to keep the solution alkaline. As long as the solution remains alkaline, corrosion is controlled and the cooling system is protected. Over time corrosion inhibitors are depleted and the corrosion protection is lost, therefore green antifreeze should be changed every two years.<o:p></o:p>
Red/Orange:<o:p></o:p>
Orange or Red antifreeze known as long life or extended life antifreeze increases the useful life of engine coolant. Long life antifreeze is also ethylene glycol based. The difference between the two colours is that Orange / Red antifreeze contains a different type of corrosion inhibitor that has a much longer life than silicates, phosphates and borates. Orange / Red antifreeze contains organic acids that protect engine parts from corrosion. Orange type antifreezes are suitable for up to five years or 100,000 miles.<o:p></o:p>
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Warning…! 
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Green antifreeze does not mix with long life antifreeze, red / orange. Never mix the two colours in a cooling system. The organic acids in orange types will cause precipitation of silicates in the green type and corrosion protection is greatly reduced. <o:p></o:p>
Bluecol U Topup: 
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It’s called top-up for a number of reasons. Bluecol U is a universal top up antifreeze coolant which is suitable for use in all vehicles (both petrol and diesel) and it will mix with all colours of antifreeze already in the radiator / expansion tank. Hence the name - Topup…!!<o:p></o:p>
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When Bluecol U is added to antifreeze already in the cooling system, the synthetic process and additive package in Bluecol U enhances and revitalises the qualities of the original antifreeze, providing exceptional all year round protection and performance in all driving conditions.<o:p></o:p>
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Bluecol U Antifreeze offers superior corrosion resistance over extended service periods, which can also be left in the system as a coolant and inhibitor against rust up to a maximum of 5 years. Bluecol U is manufactured using demineralised water which is an added bonus.<o:p></o:p>
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Summary: 
In short you have bought one of the best antifreeze mixtures on the market at a great price. I would not hesitate to use it in my MX5 if I were doing a coolant change.<o:p></o:p>
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I hope this helps, (and before you ask… No I don’t work for Bluecol).<o:p></o:p>
Mike 
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