can you put any water in a car

[VanAvery]

You can put water in your car, but only in specific systems and with major caveats. For everyday use, distilled water mixed with antifreeze/coolant is required for the cooling system. Using plain tap water, especially in cold climates, can cause serious engine damage. The only time it's acceptable to use straight water is in an absolute emergency, like a coolant leak, to temporarily prevent your engine from overheating until you can get to a repair shop.

The primary place for liquid in your car is the cooling system. Its job is to regulate engine temperature. Modern engines operate at around 195-220°F (90-105°C). A proper 50/50 mix of antifreeze and distilled water has a higher boiling point and a much lower freezing point than water alone. Using plain tap water can lead to corrosion, mineral scale buildup that clogs the radiator, and freezing in winter, which can crack the engine block.

System	Recommended Fluid	Freezing Point (Approx.)	Boiling Point (Approx.)	Key Risk of Using Plain Water
Cooling System	50/50 Antifreeze/Water Mix	-34°F (-37°C)	265°F (129°C)	Freezing, corrosion, overheating
Windshield Washer Fluid	Commercial Washer Fluid	Varies by formula	Varies	Freezing in reservoir, poor cleaning
Battery	Distilled Water (only if applicable)	N/A	N/A	Mineral damage (for serviceable batteries only)
Engine Oil	Motor Oil	N/A	N/A	Severe engine damage
Fuel Tank	Gasoline / Diesel	N/A	N/A	Engine failure, system damage

For your windshield washer fluid reservoir, you should use a dedicated washer fluid, not water. Washer fluid contains solvents to clean grime and antifreeze agents to prevent it from freezing in the lines and reservoir. In a pinch, you can use water, but it won't clean as effectively and risks freezing.

The most critical rule is to never put water in the gas tank or engine oil fill cap. Water in the fuel system will cause the engine to misfire and stall, leading to expensive repairs. Water in the oil will destroy your engine's lubrication properties, resulting in catastrophic failure. Always consult your owner's manual for the correct fluids and their specifications.

[SanHailey]

Look, I learned this the hard way. My old beater started overheating on the highway, and I dumped a couple of water bottles in the radiator to get home. It worked as a quick fix, but my mechanic chewed me out. He said the minerals in the tap water started gunking up the system. He flushed it and put in the proper coolant mix. So yeah, water can get you out of a jam, but get it fixed properly right after. Don't make it a habit.

[Harriet]

As a rule, use only what your owner's manual specifies. For the cooling system, that's almost always a pre-mixed coolant or a concentrate you dilute with distilled water. Distilled water is key because it lacks minerals that cause corrosion. The antifreeze part isn't just for winter; it raises the boiling point for summer too. Water alone is a last-resort option that should be remedied immediately by a professional.