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?
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.
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.