I put the wrong coolant in my '99 Ford Expedition and I was wondering how long I could drive it before I need to have it flushed and have the correct coolant put in?

  • What coolant is it supposed to take, and what did you put in? – anonymous2 Dec 9 '16 at 3:24
  • It's supposed to take the green kind and I put in the orange – Stacey Dec 9 '16 at 3:32
  • 3
    "Green" and "orange" aren't kinds of coolants, they are colours or coolants. Some coolants are chemically compatible yet have different colours. What did you put in there? What does the container say it's formulation is? Or which brand is it? – tlhIngan Dec 9 '16 at 5:12
  • There probably isn't a real answer for this but I rain an engine with a silicate coolant for over year by accident. It specially required non silicate coolant. I just did a very thorough flush with water and then filled with the correct stuff. The car was fine for a further few years but was scrapped for other reasons. – DizzyFool Dec 9 '16 at 13:12

It really depends on the kind of coolant that the maker specifies, the kind that was in the cooling system, and the kind that you put in.

Some coolant combinations are incompatible and, if mixed, form a sludge that greatly diminishes the cooling capacity of the system. You can't run that for long at all. As in, just don't.

On the other hand, other coolant formulations are specified for corrosion protection and you can probably run the wrong stuff for a reasonable amount of time (weeks, maybe more) without problem.

The bottom line is that without knowing the specifics:

  • The coolant specified for your vehicle.
  • Original coolant type that was in the engine.
  • New coolant type.
  • How the mistake happened – putting in the wrong coolant after a through flush is a very different (smaller) problem than mixing the two when coolant was low.

It is almost impossible to give you a meaningful answer.


No problem!

Drive as much as you like and replace the coolant whenever you have enough free time.

Most of the modern coolant liquids are ethylen glycole based formula and they could be blended without making trouble.

all types of the coolant liquids are chemically stable compound and they are not going to engage in any chemical operation easily.

  • IAT and OAT coolants are not all compatible with each other and the reaction that you get when you mix them can produce a "sludge" that can clog radiator passages. – dlu Dec 10 '16 at 7:33
  • @dlu May you please provide an example for those two formula that may blend chemically ? – Iman Dec 10 '16 at 20:22

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