Engine Coolant Basics


I was looking to buy a can of engine coolant to store in the luggage of my Triumph Tiger 800 XRx in case of emergency and ended up learning that Triumph uses a proprietary coolant called “HD4X Hybrid OAT” which is available at Triumph dealerships only. Since the closest one is in a different state, I figured I could buy a coolant with the same specification. However I ended up doing some research on the topic which has prompted me to write this.

Turns out only a third of the heat generated by the explosion of fuel in an internal combustion gets used to turn the crank shaft of the engine. Another third is ejected out of the engine through the hot exhaust gases and the remaining third gets absorbed by the engine making it hot, thereby creating the need to cool it down. Liquid cooled engines have a coolant flowing through them whose job is to transfer heat from the engine to the environment.

Coolants need to have three basic properties:
1) Should not freeze in cold climate
2) Should not boil and vaporise at operating conditions
3) Should not corrode parts of the cooling system (engine block, radiator, etc.)

Glycols are liquids that exhibit the first two properties and are used as coolants. The third property is achieved by adding chemicals called corrosion inhibitors which is where things get interesting.

There are three types of coolants: traditional, OAT (Organic Acid Technology) and Hybrid. Traditional coolants use inorganic salts as corrosion inhibitors whereas OAT coolants use organic acids. Hybrid coolants use both thereby enjoying the best of both worlds.

And now for the all important piece of information. Inorganic salts protect parts of the coolant systems belonging to older engines, whereas organic acids are good at protecting more fancy metals like aluminium and magnesium which are use in modern engines and cooling systems. So that’s why it’s important to use the right coolant to cool your engine otherwise you run the risk of slowly eroding parts of your engine and its cooling system.

So coming back to Triumph and its proprietary HD4X Hybrid OAT, the name tell me that it’s a Hybrid coolant that’s specially designed for Triumph engines and the cooling systems they use. The folks at the Triumph dealership specifically asked me not use any other coolant. They said in case of an emergency I could add upto 100 ml of mineral water to top up the coolant.

The best part of the Tiger is its wonderful engine and in matters like this, I think it’s best to go by the book. Better be safe than sorry.