How to fill your car with screen wash

Driver topping up their car screen wash bottle from blue container

For many drivers, car maintenance jobs such as filling up with screen wash are something other people do. According to various polls, anywhere between a third and a half of drivers struggle when it comes to even basic tasks to keep their car fit and healthy.

But there are some jobs that are key to safe driving and remarkably straightforward to do. Topping up the screen wash is one of those. To react safely to hazards ahead, you need to be able to see them. That’s why this simple liquid is so vital. It’s so important that not having any is sufficient reason for a car to fail its MOT. Here’s all you need to know to perform this vital DIY motoring task.

How do you know when it needs doing?

Modern cars will tell you when their screen wash is running low. As a full washer bottle isn’t fundamental to the car’s operation and running out won’t damage the car in any way, the reminder light is orange. It will usually illuminate when it’s running low rather than when it’s run out. The size of the windscreen washer bottle, and therefore the frequency that it needs to be filled, varies depending on the make and model of car. Family hatchbacks usually have between three and five-litre reservoirs.

Where is the bottle and what does it look like?

The screen wash bottle is located beneath the bonnet in the engine compartment. Its location differs from car to car. If you’re not sure exactly where it is, look in the user manual. The bottle itself is frequently hidden away with the only visible part the cap and the bottle’s neck. The cap of the reservoir is frequently blue with a windscreen and wipers symbol on it. However, the cap may be white or black.

Close up image of screen wash jets cleaning car windscreen
Using proper screen wash will prevent smearing and the washer jets getting blocked with limescale

Why use screen wash?

It sounds obvious but the primary purpose of screen wash is to clean the windscreen. Although water can technically do this, it won’t do so particularly effectively, a bit like washing up without washing-up liquid. Proper screen wash is formulated to remove the road grime, dead insects and dirt that windscreens get covered in. If you don’t remove them – and water won’t ‑ you’ll end up with smearing on the screen. In addition, proper screen wash features water softener to prevent limescale building up in the pipework and tiny squirter jets.

How much to use?

It really depends on the time of year. Part of the function of screen wash is to lower the freezing point of the water in the reservoir. In winter that temperature will need to be lower so the proportion of screen wash to water will be higher. What ratio for particular temperatures is detailed on the bottles.

How to do the mix

Frustratingly, it’s impossible to know how much screen wash you’re going to need until you’ve filled the reservoir. The car’s user manual will tell you its total capacity but you won’t know how much is already in there. We use an old screen wash container. You can then mix the liquids in that and, if you don’t need it all in one go, none will go to waste.

Where to buy screen wash from

Screen wash is widely available from supermarkets, filling stations and DIY stores as well as motor retailers and online.

Why not use washing up liquid?

Would you do the washing up using screen wash? Thought not. Washing-up liquid is designed to dissolve grease and left over food from plates and pans. What it’s made of is not formulated to be kind to a car’s paintwork.

If you’re having a problem with your windscreen washers find a garage to put it right here

Mandy Weston

Mandy is an ex-mechanic, with 22 years’ experience in the motor industry. As an in-house motoring expert, Mandy is the go-to woman for any relevant questions that our customers have; both garages and drivers. From specific problems with your car to general maintenance, Mandy is a reliable source of information and advice. Her passion for motoring is a huge factor to her success and the huge wealth of knowledge that she has. She now uses her remarkable grasp of the industry to write regular content for our readers to help drivers understand their car better, avoid being ripped off by garages and save money on their motoring requirements.