The Facts About Engine Coolant and Why Yellow - or Orange - Is The New Green experts reveal the "secret" behind coolant colors, and give timely advice about checking and replacing coolant.

Carson, CA – February 26, 2015Orange is the New Green


Its strange to think that the same stuff keeping cars in Los Angeles cool can also protect vehicles buried under massive snowdrifts in Boston. Yet it’s true: with proper seasonal maintenance, engine coolant – the combination of antifreeze/coolant and water – keeps your cooling system from corroding, boiling over and freezing! According to, just how this colorful fluid does so much is a fascinating story of chemistry and automotive innovation. 

“If there’s anything you should remember about coolant, it’s this: don’t trust the color,” said Brian Hafer, VP of Marketing for “What started out as plain old neon green fluid for all cars, has evolved from that key identifier, to today’s bright variety of colors. It’s like orange has become the new green…as well as blue, yellow and pink. Today, all these colors help define the three basic types of corrosion inhibitor packages. That’s more than a little confusing, so we wanted to break it down for car owners and add some insight on coolant safety as well.”

Coolant 101

Coolant 101: 

  1. Engine coolant is a mixture of antifreeze/coolant, de-ionized water, corrosion inhibitors, and dyes. A proper mixture is important because it prevents corrosion of the cooling system components, raises the boiling point and lowers the freezing point. That’s how one fluid can protect Bostonians in February and Angelenos in August.
  2. Most antifreeze/coolants contain ethylene glycol (EG) – a slightly sweet smelling chemical that is poisonous to animals and humans.  Propylene glycol (PG), which is less hazardous, is also used. Both are still toxic when drained, and should be disposed of properly.
  3.  EG and PG raise the boiling point of coolant, and lower the freezing point. The glycol fluid by itself doesn’t, however, carry heat away effectively. That’s what water is for, and why diluting antifreeze/coolant with water is so important.  A 50/50 mixture is normally recommended and often sold premixed.
  4.  The corrosion inhibitors in engine coolant will break down over time, which is why you should change it periodically. Follow the manufacturer’s recommendations for the type of fluid used and the service interval. 

Coolant Technologies 

The Three Basic Coolant Technologies:

  • IAT: Inorganic Acid Technology is the traditional green stuff that is pretty much only used on older cars that predate the late nineties. The lifespan of traditional coolant is about two years.
  • OAT: Organic Acid Technology is used today because it offers silicate-free protection of all metals, and for a longer period of time: it’s the long life (LLC) or extended life (ELC) coolant and has a service life of five years or 150,000 miles. Colors are mostly red and orange, but also green, pink and blue.
  • HOAT: Hybrid Organic Acid Technology. This is also used today, and is usually orange or yellow. A mix of IAT and OAT, the orange cocktail – and only the orange -- contains 10 percent recycled coolant.   

About Coolant Colors

It’s likely that manufacturers of coolant could have simply replaced green with green. But there’s really no fun in that, right? Some say General Motors started it with the neon yellow hues of Dex-Cool, and others point fingers at VW and Audi for bringing over the coolant that had been used for years in Europe.


Changing Coolant

Frequently Asked Coolant Questions

  • When should I check my coolant levels? It’s generally a good idea to inspect the coolant level at every oil change. Most of today’s cars operate with coolant good for 100,000 miles or more – but severe driving or other factors may change that. So, if you live in Boston, when the snow melts make sure you check your coolant along with other important fluids. Conversely, cars in southern California rarely get a break from hot temperatures and traffic jams, so checking the level and color of coolant may help prevent overheating. Best tip: the next time you open the hood, check the coolant level in the reservoir and give your radiator hoses a squeeze.
  • Can I just add water to my radiator? ONLY in an emergency! Adding water to already-diluted coolant encourages rust and corrosion.
  • Do I have to mix antifreeze/coolant with water in a 50/50 mix? That’s the ideal dilution for most climates.A 50/50 mixture represents a compromise between cooling efficiency and the ability to prevent the mix from freezing. Always follow the manufacturer’s recommendation if you live in an area with extreme temperatures.
  • Can I just replace yellow coolant with yellow coolant? No. Check your owner’s manual and make sure you use the recommended type of coolant.
  • Can I replace my own coolant? Yes, but follow common sense safety procedures, such as wearing safety glasses. Most importantly, keep a sharp look out for coolant spills. The fluid has a sweet sort of smell and taste to it, which may attract pets. Even a small amount of coolant ingested by the family dog or cat can have serious consequences.