Worn blades smear dirt across the glass and visibility drops sharply, especially at night, in rain and sleet. Blades last roughly 18-24 months, but they should be changed as soon as they streak, squeal or judder.
Both heat and frost age the rubber: in summer it dries out in the sun, in winter it hardens and tears on ice. The best time to check blades is late summer or mid autumn, before the rain and cold set in. Changing them takes ten minutes and no tools.
What you will need
Important: Hold the arm while the blade is off: if it snaps back onto the screen under spring pressure, the glass can crack. Keep lubricants off the windscreen and the wiper rubber.
Step 1
Choose the right blades
Length and fitting type depend on the car, and the driver and passenger blades are often different sizes. The sizes are in the owner's manual, and a motor factor can look them up by make and year. Replace blades as a pair so both work the same.
Step 2
Remove the old blade
Lift the arm away from the glass until it locks, or hold it carefully. The new blade packaging usually shows a diagram for your fitting type. Most often you press the release tab at the joint and slide the blade off the arm hook. On some cars you need to put the wipers in service position or open the bonnet to reach the arms.
Lay a folded towel on the glass under the arm in case it slips from your hand.
Step 3
Fit the new blade
Fit the new blade in reverse order: slide the adaptor onto the arm hook and press until it clicks, without knocking it. If the metal end of the arm is rusty or stiff, put a drop of WD-40 Smart Straw on it through the thin straw, with the glass covered by a cloth, and wipe off the excess at once. Lower the arm gently onto the glass.
Step 4
Top up the screenwash
Check the washer reservoir and top it up. Summer fluid is fine in warm months, but from autumn use a frost-proof screenwash with a margin below the expected temperature. An empty reservoir when a lorry sprays your screen is a real safety risk.
Step 5
Test the wipers
Run the washers and wipers at each speed. The blades should sit evenly along their whole length, run quietly and clear water without streaks. If one blade judders, check it has fully clicked onto the arm.
Tip: To make new blades last, wipe the rubber edge with a damp cloth once a week and never run the wipers over a frozen screen. Before a frosty night you can lift the arms off the glass.
What next
Check the blades twice a year: in autumn before the cold and in spring after winter. If the wiper still lifts or will not move after a new blade, the fault is in the arm or motor and needs a separate repair guide. Keep WD-40 Multi-Use in the boot for door hinges and locks.
These uses come from the experience of WD-40 users in many countries. Always follow the instructions and warnings on the product label.
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