My husband noticed out coolant level was low and added in green on top of orange. He didn't know the coolants shouldn't mix. Now I'm worried that our car is ruined because of this. I know they can do a transmission flush but will the sludge like consistency be fixed? How expensive is it usually? We aren't driving it until we have to go to the mechanics on Monday but I want to know what we're in for.

  • Welcome to Motor Vehicle Maintenance & Repair! Apr 18, 2020 at 13:01
  • They are pretty much just different dye colors used by different manufacturers for ethylene glycol. No significant difference. Apr 18, 2020 at 15:16

3 Answers 3


"Green" coolant is usually considered a typical coolant. It should get changed out about every two years. "Orange" coolant implies Dexcool, which is the stuff used in GM vehicles and is a long life coolant. It should be replaced about every five years or 150k miles. If you mix the two together, there's no real issue, but you shorten the life of the coolant to that of the green coolant, which means it would need to get changed sooner. While you cannot mix all coolants together, these two (if typical) can be mixed without issue.

Mixing coolant is not a death sentence for you engine or car. You should, however, get it changed out to the coolant which should be in there as soon as possible just to alleviate any long term issues. It is pretty common to have your coolant flushed which will solve your issue.

There's two things you can do:

  1. You can flush it yourself. There are kits you can use to do this. The only thing about this is you have to have a way to catch and recycle the coolant which comes out. You don't want this stuff in the drain system as it is toxic to animals (including humans).
  2. Take it to a reputable mechanic or service shop and have them flush it for you. They'll actually have the means to recycle the coolant properly. Yes, it costs a bit more than doing it yourself, but is probably worth your time in the long run.

The expense of either solution is dependent upon where you go and where you live. It would be too broad of an answer to try and give you a real response to this.

Something to consider which got you here in the first place is, why was it low on coolant? Once you get the system flushed, you may want to be looking at whether the system is leaking. Look for obvious things, like spots in the garage or driveway where the vehicle is parked overnight.


Early on when coolants changed to different types you could not mix types, they would gel. These days all coolants can intermix without issue as coolant manufacturers made coolants compatible with any other type of coolant, so you are safe with mixing these days.

But as Paul stated doing a cooling system flush is part of regular maintenance as coolant breaks down after 100-150K miles or so.

Here is one radiator I replaced back in the day, pulled the radiator tank to show you what happens when coolant gels. Destroyed many engines due to gel plugging radiator cooling tubes and causing overheating of the engine.

enter image description here


They can do a cooling system flush and it'll be fine. It takes a while for mixed coolant to do damage. You should be fine with a monday flush. Flushes run less tha $200.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .