There are many formulations for coolant as each manufacturer has their specific formulations, however in the United States, there are three main type of engine coolant: Original Green Inorganic Acid Technology (IAT), Organic Acid Technology or OAT-Based, and Hybrid OAT G-05 and G-11 coolants. You may ask “why does this matter to me, I have a 1970 Chevelle, the old green stuff is fine.” If you have the original engine, then sure, you would be right, but if you have LS swapped that Chevelle?
This myth is one of the worst there is, as the thermostat does not have any control over the operating temperature of your engine. Your engine is going to run as hot as it is going to run based on the cooling system parameters. A properly designed system will maintain the temperature in a safe range. The only thing the thermostat does is open and close at a specific temperature, it is actually regulating the minimum temperature, not the top end. A 160-degree Tstat begins to open around 135-140 degrees and is fully open at 160. When the temps fall below 160, the Tstat begins to close until the temps rise again. If you have too high of a tstat, your engine will get up to temp faster, but you are closing off some of your cooling range, going to a cooler temp unit will only open the flow faster.
Moving beyond the radiator, the rest of the system is just as important. The biggest mistake many gearheads make with their cooling system is the fan. Mechanical fans are just fine, but they eat horsepower and are not controllable. Electric fans are the best option for any car that is not restrained by originality. Regardless of the fan style, all fans should be shrouded, especially mechanical fans. Without a shroud, a mechanical fan is just stirring up the air around it, there is little draw through the radiator at all. With a shroud, the fan generates a vacuum, pulling air into the radiator. This is only important below 40 mph, once the vehicle is moving 40 or faster, the natural airflow takes over.
f you have ever been to a parts store, you probably noticed about a million radiator caps. While some of this is due to OEMs not using a standard cap size (Asian cars have very small caps for example), there is also a difference in the pressure relief. Heat means pressure, and your cooling system has a limit on how much pressure it can contain; this is where the cap relief valve vents to purge that excess pressure. When you get steam pouring out from under the hood, that is the cap venting.
