Orange antifreeze should not be mixed with green antifreeze because they are not compatible. If mixed together, these two types of antifreeze form a cloudy substance and precipitation that can decrease the coolant's useful life properties.
Although both the green and orange antifreeze are ethylene glycol-based, the difference between them is that they contain different corrosion inhibitor ingredients or additives. While orange antifreeze contains organic acids, green antifreeze has additives, such as silicates, borates and phosphates. The interaction of these different antifreeze types causes the formation of silicate precipitation, which has an impact on corrosion protection.
Another difference between these two antifreeze types is that orange antifreeze has a longer useful life that the green type. Orange antifreeze has a useful life of 5 years, whereas green antifreeze is good for up to 3 years. Orange antifreeze is referred to as an extended-life antifreeze.