Flammability of Engine Coolants

Evans is occasionally asked how the flammability of Evans Waterless Coolants compares with the flammability of conventional antifreeze mixtures that are generally half glycol and half water. On balance, Evans Waterless Coolants are not more fire-prone than standard water-based antifreezes.

When one researches the causes of vehicle fires, there are these conclusions:

  • Neither antifreeze concentrate (without water) nor water-glycol antifreeze coolant is likely to be a first-fuel in a vehicle fire, but both can be ignited.
  • Many factors have to be just right for ethylene glycol (EG) to be ignited, and it is unlikely that all of the factors present in laboratory tests will be present in a vehicle to enable combustion to occur.
  • “Ideal” conditions are present in a laboratory when the flash points or fire point of liquids are determined and one needs to be careful in extrapolating the results to vehicle situations.
  • For ignition to happen under non-ideal conditions, the hot surface metal temperatures for auto-ignition to occur (one mode of ignition) need to be higher than would be present under normal engine operation.
  • In some instances, the temperatures need to be higher than even those seen in malfunctioning engines and in vehicles in which the engine has been overloaded for an extended period of time.
  • Ignition of EG by a vehicle’s electrical system is unlikely because of the very specific circumstances that must exist.
  • Although the presence of water in water-based antifreeze may provide some small measure of a quenching effect on an open flame, the water portion is generally short lived, as it is quickly vaporized and what remains is primarily glycol, which can ignite.
  • One of the most important conclusions drawn by forensic investigators of vehicle fires is: Ethylene glycol coolants will not auto-ignite on the metal surfaces in a motor vehicle and cause a vehicle fire, except under very specific and unlikely conditions.

Dispelling Myths:

Most experts agree that water-based antifreeze is just as flammable as antifreeze concentrate under the right conditions. Timothy C. Finley is a Vehicular Forensic Reconstruction Specialist. His research has helped fire departments, police, and insurance companies determine what caused a fire. When Mr. Finley was asked about the flammability of antifreeze his response was as follows:

“As a forensic investigator of vehicle fires for nearly twenty years, the question of flammability of coolant has arisen many times and has been the issue of a number of lawsuits in the past. In the mid 80’s I observed a number of vehicle fires whose causes could only be explained by the ignition of engine coolant. At that time, there was no data available on the subject. I therefore chose to conduct testing to determine if pure antifreeze or antifreeze mixed with water in a 50% solution (coolant) would ignite or burn. I found that both would auto-ignite (ignite outside the presence of a spark or flame) on a hot surface. Surface temperatures of 650 degrees F to 750 degrees F would cause auto-ignition. Vapors at lower temperatures would ignite from a spark or flame. Heat sources containing more mass facilitated the auto-ignition process. I have repeated this testing a number of times over the years.”

From: Engine Coolant is it Flammable? http://garrett-engineers.com/2005/10/what-auto-fluids-burn

Cleveland Open Cup Test of Ethylene Glycol-Based Engine Coolant Mixtures Water % V.S. Flash Point

Percentage Ethylene 
Glycol (%)

Percent Water (%)

Boiling Point (°F)

Flash Point

Flame Point

Volume Loss Flash to Flame Point (ml)



360 to 365

254 to 260

254 to 260




284 to 286

255 to 262

262 to 275




247 to 248

287 to 288

290 to 293




224 to 227

286 to 288

292 to 296

         15 to 20



226 to 227

286 to 289

293 to 294

         25 to 30



208 to 209

287 to289

295 to 296


 Evans Advantage of a Low System Pressure:

A positive benefit that Evans Coolant provides as it relates to flammability comes from the reduced system pressure associated with the use of waterless coolants. Unlike their water-based antifreeze counterparts, waterless coolants operate with minimal system pressure, meaning that if the cooling system were compromised, hot coolant would not violently erupt, as would be the case with typically pressurized water-based coolant. If the leak were just a pinhole, there would be no atomized spray, as would be the case if the pressure were at typical water-based coolant values.

The vapor pressure of 50/50 weight percent EG and water mixture at 230F:  838 mm Hg

The vapor pressure of an Evans Waterless Coolant at 230F:                           24.6 mm Hg                           

Based on third party flash point testing and years of anecdotal experience, waterless coolants present no more danger as it relates to flammability than water-based coolants under the same conditions. At its core, Evans Cooling Systems, Inc. is a technology based company whose goal is to produce products that are safe, effective and that provide a real benefit to the end user.