Do I Need to Use Up the Old Windshield Washer Fluid Before Refilling?
2 Answers
It is not necessary to use up the old windshield washer fluid before refilling. Here is some relevant knowledge about replacing windshield washer fluid: Windshield washer fluid can be mixed: The main function of windshield washer fluid is to clean the glass and prevent the washer reservoir from freezing. Although it is a chemical product, the formulas of different brands are basically the same, so mixing them will not cause any violent chemical reactions. Adding new windshield washer fluid: Many car owners only replace the windshield washer fluid when it has already run out. By the time they refill it, the washer reservoir is empty. In other words, the old windshield washer fluid has already been "poured out," so you can safely add new fluid.
Just refilled the windshield washer fluid for my old car a couple days ago, and realized there's no need to deliberately use up the old fluid. You can simply pour in the new one directly – I've even mixed summer formula with winter antifreeze versions without issues, and it still sprays clean. But if there's sediment at the bottom of the reservoir or you previously used a cheap off-brand fluid, it's better to drain the old completely before adding fresh. Once I skipped cleaning and the nozzles got clogged for almost two weeks – cost me dozens at the car wash to unclog. Pro tip: shake the fluid container before refilling; the sloshing sound tells you roughly how much is left.
