silicate: a compound containing silicon and oxygen, also known as Silicon dioxide (SiO2)
Silicates and phosphates were additives used in most older formulations of coolants. The newer types of coolants specified are sometimes required to be silicate and phosphate free, especially those using organic acid technology.
silicate free coolant is recommended for all latest engine
only ethyline glycol base coolant is recommended
Toyota's LLC is silicate, phosphate, nitrite and amine free
mostly depends on the water you put along with it - if you use heavily mineral hard water you need silicate free coolant
What is coolant
When draining the coolant, keep in mind that cats and dogs are attracted by ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a leak-proof container. To avoid injuries from scalding fluid and steam, DO NOT remove the radiator cap while the engine and radiator are still HOT. The best way to dispose of coolant is through an approved recycling center.
Ethylene glycol
Coolant in most late model vehicles is at least 50-50 mixture of Ethylene glycol and water. This mixture in older vehicles was required not only in the winter to prevent freezing, but also to prevent corrosion in aluminum cooling systems, and to provide lubricants to the water pump. Modern vehicles with air-conditioning must also use it in the summer as well.
Late-model vehicle manufacturers also require their engines to run at a higher temperature because it results in better engine efficiency and improves the effectiveness of emission control devices. This temperature is controlled by the thermostat, most of which are in the 192°F (89°C)-195°F (91°C) range.
Good quality antifreezes also contain water pump lubricants, rust inhibitors, and other corrosion inhibitors along with acid neutralizers. Ethylene glycol antifreeze mixtures should not remain in the cooling system beyond one year.
Propylene glycol
Appearing in the early 90's a new, less-toxic antifreeze/coolant emerged. This is a propylene glycol base. As compared to ethylene glycol, propylene glycol is less toxic and safer for humans, pets, and wildlife in the environment. Its coolant and engine protection properties are similar to the ethylene glycol coolant listed above. Most of the coolant providers now offer a choice between ethylene glycol- or propylene glycol-based products.
Silicate-free coolant
The cooling systems on some 1996 and later vehicles were originally filled with silicate-free coolant. The fluid is easily identified because of its orange color (instead of the green we have come to expect from most types of ethylene glycol antifreeze). If your cooling system is filled with DEX-COOL® or other silicate-free coolant, then no periodic service is required, other than fluid level checks, for 100,000 miles (160,000 km) or 5 years, whichever comes first. However, if you add a silicate coolant to the system (even in small amounts) premature engine, heater core or radiator corrosion may result. In addition, the coolant will have to be changed sooner (12,000 miles (19,300 km) or every year, just like other vehicles not using DEX-COOL® or other Silicate-free coolant).
