Accidentally added RV antifreeze to radiator (blue ford escort, 1998) - approx 1/3 gallon. Radiator fluid was low; existing fluid included vehicle antifreeze. Will this cause problems? If I need to have the system flushed, how soon does it need to happen? Thanks!! Dody

To properly answer your question we would have to know which RV antifreeze you added, and which type of antifreeze was originally in your car.

RV antifreeze comes in two general varieties – those based on ethanol and those based on propylene glycol or ethylene glycol. Ethanol-based antifreeze is not recommended in your car because it can affect rubber seals.

The other type should be OK provided it is compatible with your original antifreeze. If you know you had the general-purpose Prestone-type antifreeze, you should be OK. Leave it alone. If you had some of the weird red stuff or Dexcool maybe, I would advise a flush sometime soon. Not urgent.

Thanks Steve, it was a propylene glycol. I really don’t know my original antifreeze; so I will get the system flushed, but at least now I know the car can be moved without ruining something! Thanks again…

Yes, you can drive your car. Nothing will be damaged. The only reason we advise against mixing certain antifreezes is that the anti-corrosion inhibitors are incompatible. But you still have full antifreeze properties, and the engine doesn’t mind the mixture. You have maybe a year to replace.

Propylene glycol is compatible with the antifreeze in your car, so there is no urgency to get it flushed, and I would not flush it anyway. When the maintenance schedule calls for it, just do a drain and refill, make sure to drain the block as well as the radiator.

The fact that you needed to add coolant is a bigger concern. You should first check for slow leaks and fix them first.