On a modern automotive engine, if the system is flushed with water, is it safe to use regular non-OAT ethylene glycol coolant and then continue to replace it at the defined interval (2 years for regular)?

For cases where it is impossible to find the information from manufacturer etc.

Specifically, if factory fill was an OAT product, do we lose anything other than the extended service period by switching over to a conventional coolant?

I'm not so sure about silicates and phosphates as this information is missing from the coolants available to me but I am also interested if this is important.

  • Do you know what vehicle manufacturer is? It may be possible by going to coolant manufacturers to work out what the vehicle ought to be filled with. Oct 30, 2018 at 11:11
  • Related question, maybe even a dupe
    – Zaid
    Oct 30, 2018 at 12:12
  • I believe for the most part you could get away with it ... the only problem is with the "off vehicle" where it truly does matter. Take for instance. I have an '03 Honda. It came with the Blue coolant. So many of these Hondas would get a head gasket leak by not using the Honda Blue stuff ... doesn't happen right away, but it happens. Look here on MVM&R and see how many of the 01-05 Civics have overheating issues and I'd lay money it is directly related to this issue. It's what happened to mine. Putting the wrong coolant in a car can have adverse effects. Which ones exactly is beyond me, though. Oct 30, 2018 at 12:53
  • Most suppliers of coolant products have guide books so you look up year, make, model and engine and it tells you... Granted it may not list a Bentley from the first year of production but most other vehicles are in....
    – Solar Mike
    Oct 30, 2018 at 15:05
  • @SteveMatthews I've done that, most say OAT but I don't trust them as they tend to say their coolant can be mixed with any existing coolant - which is untrue.
    – DizzyFool
    Oct 31, 2018 at 8:57


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