Using the wrong antifreeze in your car can lead to engine dammage. The chemicals in the coolant may have a corrosive effect on the different types of allows in the engine. Also, different types of coolant DO NOT mix. If you fill a bottle with half green coolant and half orange coolant and shake it they'll appeaqr to mix but when you let it sit they will seperate again. I've never heard of blue coolant but I can only imagine it won't mix either. The way engines are built nowadays you really can't just put in any fluids, putting in the wrong tranny fluid, engine oil, coolant or whatever can lead to severe dammage and expensive repairs. Of course you can use whatever windshield washer you want though!!!