By Peter Woyciesjes, Ph.D.

As we face the winter of 2016, we can reflect back on the prior year as the poster child for the importance of preparedness. States west of the Mississippi river experienced unusually warm weather. Conversely, February 2015 was one of the coldest Februarys on record in many Midwest and Northeast cities. All but four states east of the Mississippi placed within their 10 coldest Februarys since 1895. Arctic sub-zero temperatures and double-digit wind-chills left many busses stranded or with incapacitated equipment.

For many of those stranded during the winter cold snap, it was decisions made about what to do (or what not to do) with their antifreeze/coolant systems that may have sealed their fate.

Winter is coming

At a glance, coolant maintenance may seem to be as simple as pouring in new coolant. However, given the vast number of new antifreeze/coolant technologies and formulations, making decisions regarding their maintenance is a very serious matter that can potentially affect the bottom line of any fleet. Ask anyone who may have been stranded or stuck in the shop during any brutal winter cold snap.

The primary components of antifreeze, both glycol and water, can freeze; however, a combination of both has the ability to prevent freezing to a lower temperature.

While recognizing glycol levels in antifreeze/coolant is essential to maintaining a properly operating heavy-duty vehicle, it is by no means less of a concern than corrosion within the engine. Responsible testing recognizes coolant has key protective characteristics that can minimize additional issues such as corrosion or scaling buildup.  During extreme temperatures, fleets are not thinking so much about corrosion protection as they are trying to make sure the necessary percent of glycol is correct in their formula. Corrosion protection is a daily concern for the heavy-duty engine, and freezing concerns tend to be seasonal.

Inspection essentials

A solid practice for antifreeze/coolant maintenance would be to take the opportunity to check the overall effectiveness of coolant while also checking for seasonal freezing protection.

There are three steps for such an inspection:

  1. Test your glycol for freeze-point.
  2. Test for inhibitors to make sure you’re still getting the correct corrosion protection.
  3. Make sure you’ve got the right volume in your cooling system so there are no air pockets.

Air entrapment in the engine is a serious problem for any engine. Seasonal cold weather testing is the ideal time to make sure your engine is full and topped off.
A routine loss of coolant due to leaks and other maintenance issues can be expected. In these cases, topping off with the appropriate 50 percent pre-diluted coolant is ideal. If an engine has encountered cooling system failure, draining and replacing the coolant with a fresh fill of a quality coolant is recommended.
I would not recommend that coolant collected from a leaking system or a system being drained be reused. Given everything within the engine that relies on the cooling system, it is much safer to refill the system with a fresh batch of antifreeze/coolant.

Antifreeze/coolant should:

  • Provide freezing protection to the lowest temperature encountered.
  • Provide effective inhibition of corrosion for all cooling system metals through a wide range of temperatures.
  • Provide efficient transfer of engine heat to help control critical metal temperatures.
  • Maintain optimum engine temperature for fuel and lubrication efficiencies.
  • Increase the cooling index to help prevent boil-over and over-heating failures.
  • Unless routine testing reveals a change is needed earlier, following engine manufacturer guidelines is the best practice for ensuring appropriate antifreeze/coolant protection.


In many areas of the country, driving in severe cold and snow are an unavoidable fact of life. Bus fleets of all types have schedules that must be met and the only way they can avoid breakdowns that will inconvenience their riders is if their heavy duty engines are maintained properly.  While it’s true that effective antifreeze/coolant maintenance is not just a seasonal concern, winter’s wrath and the extreme demands of harsh weather always elevate the importance of cooling system maintenance to the forefront.

Peter Woyciesjes, Ph.D, is the worldwide RD&E manager, coolants at Prestone Products Corporation. Prestone Products Corporation manufactures and markets Prestone® antifreeze/coolant and related products. For more than 85 years, the Prestone name has provided customers with high-quality products, including one of the leading brands of antifreeze/coolant. Visit www.PrestoneCommand.com.