Prices in this table come from Amazon and are refreshed at least once a day, with the date of the last update under the table. The cost-per-use and running-cost figures on this page use prices Look Into read on 4 November 2026, so they can differ from today's price.
As an Amazon Associate, Look Into earns from qualifying purchases. Product prices and availability are accurate as of 4 November 2026 10:26 am and are subject to change.
The short answer (prices checked 4 November 2026)
- Cheapest frost protection: AA All Seasons screenwash tablets, £8.10 for 8 tablets that make up to 40 litres, effective to -4°C. That is 20.25p a litre, or 5.06p for each litre and each degree of protection.
- Coldest protection: Prestone Extreme concentrate 5L, £13.25, which the listing rates to -23°C used neat. Neat that is 265.0p a litre, or 11.5p per litre per degree.
- No mixing: Prestone Screenwash Ready to Use Winter 5L, £6.50, rated to -10°C straight from the bottle. 130.0p a litre, 13.0p per litre per degree.
- Cost of filling one 4.5 litre washer bottle at each product's coldest rating runs from 91p to £12.60. Same reservoir, same job, 13.8 times the money.
- The audit finding: of the first 20 unsponsored listings for "screenwash", 13 quote a freezing point and 4 state any dilution ratio. One publishes the temperature at more than one dilution.
Screenwash is in the charts again. On 4 November 2026 Prestone's Ready to Use Winter 5L sat at number 3 in Amazon UK's Automotive best sellers and CarPlan's All Seasons ready mixed 5L at number 12, the two of them bracketing the first proper frosts. Buying some is easy. Working out which bottle gives you the most protection for the money turns out to be harder than it looks, because the number on the front of the bottle and the number that decides whether your washers work on a cold morning are usually two different numbers.
Prices and specs last checked by Look Into on 4 November 2026 · next check 30 December 2026 · how we picked
The two-dilution problem, and why the law cares
Start with what you are actually required to have. Regulation 34 of the Road Vehicles (Construction and Use) Regulations 1986 says that a vehicle which must have a windscreen wiper must also carry "a windscreen washer capable of cleaning, in conjunction with the windscreen wiper, the area of the windscreen swept by the wiper of mud or similar deposit". Paragraph 6 of the same regulation adds that wipers and washers must "at all times while a vehicle is being used on a road be maintained in efficient working order and be properly adjusted".
The MOT turns that into a pass or a fail. Section 3.5 of the MOT inspection manual for private passenger and light commercial vehicles lists one washer defect, "windscreen washers not working or not providing sufficient fluid to clear the windscreen", and categorises it as Major. A Major defect is a fail. A reservoir of frozen water provides no fluid at all, so the thing standing between you and that defect on a January morning is the freezing point of whatever you last poured in.
Now look at how that freezing point is advertised. A concentrate has two headline claims, and they belong to opposite ends of the bottle's life. The temperature is almost always the neat figure. The value claim is almost always the summer ratio. Prestone Extreme concentrate makes both in the same set of bullet points: it "helps melt frost and light ice down to -23°C when used neat", and "a 5 litre bottle makes up to 100 litres of screenwash at the appropriate dilution". Both are true and they cannot both apply to the same pour. Used neat the bottle holds 5 litres and costs 265.0p a litre. Stretched to 100 litres it costs 13.25p a litre, at a temperature the listing never states. One bottle, one price, a twenty-fold spread depending on which of its own claims you read.
Autoglym is the one listing in the twenty we read that closes the gap, and what it shows is the reason the gap matters. Its Ultimate Screenwash listing publishes the whole ladder: 1:0 gives -45°C, 1:1 gives -25°C, 1:2 gives -14°C, 1:4 gives -6°C, 1:9 gives -3°C and 1:15 gives -1°C. The headline on the same listing is "ideal for winter weather down to -45 degrees". The dilution that listing itself calls Winter Dilution is 1:4, and 1:4 is rated -6°C. The difference between the number in the sales copy and the number at the maker's own winter mix is 39 degrees.
Nothing here is against the rules. No regulation requires a screenwash listing to state its freezing point at the dilution a British driver would use in November, and Autoglym publishing the ladder is a courtesy rather than a duty. It does mean the only honest way to rank these is to price the protection you can actually get, at a dilution the listing itself names, and to say which number came from where.
How we picked these
We read the first 20 unsponsored results for "screenwash" on amazon.co.uk on 3 November 2026 and opened every one of those 20 product pages. For each we recorded what the listing states inside the product title, the feature bullets, the technical specification tables and the product description, and nothing outside that scope. Then we worked out two figures for every candidate: the price of one litre of fluid at the coldest protection the listing claims, and that price divided by the number of degrees below zero it claims. Ready to use products get their bottle volume. Concentrates get the volume their own stated dilution produces, or the neat volume where no ratio is given, and we say which applies in each case.
Look Into has not handled these products: every figure comes from the maker, the listing or a named source, read on the date shown. Prices are the buy box price read on 4 November 2026 and will have moved since.
At a glance
| Product | Price | Usable litres | Coldest rating | Per litre | Per litre per degree |
|---|---|---|---|---|---|
| AA All Seasons tablets, 8 pack | £8.10 | 40.0 (as stated) | -4°C | 20.25p | 5.06p |
| Prestone Extreme concentrate 5L | £13.25 | 5.0 (neat) | -23°C | 265.0p | 11.5p |
| Prestone Ready to Use Winter 5L | £6.50 | 5.0 (ready mixed) | -10°C | 130.0p | 13.0p |
| Rain-X Concentrated 5L | £12.95 | 5.0 (neat) | -15°C | 259.0p | 17.3p |
| CarPlan All Seasons ready mixed 5L | £4.50 | 5.0 (ready mixed) | -4°C | 90.0p | 22.5p |
| Autoglym Ultimate 500ml | £7.00 | 2.5 (at its own 1:4 winter mix) | -6°C | 280.0p | 46.7p |
The six we would buy
Best overall
AA Car Essentials All Seasons Screenwash Tablets, 8 pack
£8.10 on 4 November 2026 · makes up to 40 litres · effective to -4°C · 20.25p a litre · 5.06p per litre per degree
Eight tablets, each one dropped into the washer bottle and topped up with water, which the listing says makes up to 40 litres. That works out at 20.25p a litre against 90p for the cheapest ready mixed bottle, and because the tablet is a fixed dose there is no ratio to get wrong. On the measure that matters here, money for each degree of frost protection, it comes in at 5.06p and nothing else in the twenty gets close. It also solves the boot problem: eight tablets fit in a door pocket and 40 litres of ready mixed would not fit in the car.
The catch: -4°C is the ceiling, not a starting point, and a British cold snap goes past it most winters. "Up to 40 litres" is a maximum rather than a promise, and dropping a tablet into a reservoir that still holds half of last month's fluid gives you a mix nobody can put a number on. Buy it for October and March, not for a hard frost.
Best for a hard frost
Prestone Extreme Screenwash Concentrate 5L
£13.25 on 4 November 2026 · -23°C used neat · 265.0p a litre neat · 11.5p per litre per degree
This is the one to keep in the garage for the week the forecast turns. The listing rates it to -23°C used neat, the coldest claim in the twenty, and even at the full neat price of 265.0p a litre it is the best value per degree of any liquid here at 11.5p. Poured neat into a 4.5 litre reservoir it costs £11.93 to fill, which is a lot for screenwash and not much for the difference between driving to work and scraping at a frozen jet.
The catch: The -23°C figure holds only neat, and neat is the expensive way to use a concentrate. The same bullet points claim the bottle makes up to 100 litres "at the appropriate dilution" without saying what that dilution protects to, and the pack is the only place the ladder appears. You are buying one of two very different products depending on how you pour it.
Best for no mixing
Prestone Screenwash Ready to Use, Winter Formula, 5L
£6.50 on 4 November 2026 · -10°C from the bottle · 130.0p a litre · 13.0p per litre per degree
The bottle sitting at number 3 in Automotive on the day we checked, and the easiest honest answer in the category. It states that it melts ice down to -10°C, there is no ratio to read and no temperature hiding behind a dilution, so the number on the label is the number in your reservoir. At 13.0p per litre per degree it is third on our measure while asking nothing of you beyond unscrewing a cap, and £5.85 fills a 4.5 litre bottle with protection that covers a normal British winter night.
The catch: At 130.0p a litre most of what you carry home and most of what you pay to have delivered is water. Five litres of ready mixed takes up the same boot space as a concentrate that would make twenty times as much, so this is convenience bought at a real price rather than a bargain.
Best for rain repellent
Rain-X Concentrated Screenwash with Rain Repellent 5L
£12.95 on 4 November 2026 · -15°C · 259.0p a litre neat · 17.3p per litre per degree
Rain-X is here for the repellent rather than the maths. The listing claims protection down to -15°C and the formula leaves a water beading layer on the glass, which is the one feature in this group that changes anything about driving in the wet rather than the cold. Treated as a neat winter fluid it costs 259.0p a litre and 17.3p per litre per degree, which puts it mid-table.
The catch: Nowhere in the title, the bullets, the specification tables or the description does this listing give a dilution ratio, while telling you the concentrate "can be diluted to suit Spring and Summer weather". That leaves the -15°C claim attached to no particular mix, so the only figure you can stand behind is the neat one, and neat is how we have priced it.
Cheapest bottle on the shelf
CarPlan All Seasons Ready Mixed Screen Wash 5L
£4.50 on 4 November 2026 · -4°C · 90.0p a litre · 22.5p per litre per degree
At number 12 in Automotive and £4.50 for five ready mixed litres, this is the cheapest way to leave the shop with screenwash in your hands, and the listing is clear about what it is: "skip the hassle of dilution and pour it directly into your washer bottle", with winter protection stated at -4°C. If your car lives in a garage in a mild part of the country it will do the job all winter and you will never think about it.
The catch: That -4°C is where our measure turns on it. At 22.5p per litre per degree it is the second dearest protection on this page, nearly twice the Prestone Extreme figure, and -4°C is the thinnest frost margin here, matched only by the tablets. The £4.50 is real and so is the -4°C.
Best for knowing what you bought
Autoglym Ultimate Screenwash, concentrated, 500ml
£7.00 on 4 November 2026 · -6°C at its own 1:4 winter mix · 280.0p a litre · 46.7p per litre per degree
This is the only listing of the twenty that tells you the whole truth, and it earns the place on that alone. It publishes six rungs of its own ladder, from 1:0 at -45°C through 1:1 at -25°C, 1:2 at -14°C, 1:4 at -6°C and 1:9 at -3°C to 1:15 at -1°C. Nobody else in the category gives you a way to work out what you will actually get, and if you want -25°C you can mix it 1:1 and know you have it.
The catch: Transparency and value are separate things. Mixed at the ratio Autoglym itself labels Winter Dilution, 500ml makes 2.5 litres rated to -6°C, which is 280.0p a litre and 46.7p per litre per degree, the dearest protection on this page and 9.2 times the tablets. The headline on the listing is -45 degrees, and that is the neat figure, 39 degrees colder than its own winter mix.
What 20 screenwash listings actually tell you
On 3 November 2026 we read the first 20 unsponsored results for "screenwash" on amazon.co.uk and opened all 20 product pages. The counts below cover only the product title, the feature bullets, the technical specification tables and the product description. Anything printed on the physical bottle, or held on the maker's own website, is outside the scope and is not counted.
- Quote a freezing point somewhere in that scope: 13 of 20.
- State any dilution ratio in that scope: 4 of 20.
- Publish a freezing point for more than one dilution: 1 of 20, which is Autoglym.
- State a freezing point while giving no dilution ratio at all: 5 of 20, which includes Rain-X at -15°C and one 5 litre concentrate at -12°C.
- Tie the freezing point explicitly to neat use: 2 of 20, Prestone Extreme and one JOVS concentrate at -24°C.
- Describe themselves as ready to use, ready mixed or needing no dilution, so that the stated temperature is the usable one: 9 of 20.
Put plainly: thirteen listings give you a temperature, four give you a ratio, and one connects the two. For a ready mixed bottle that does not matter, because there is only one dilution. For a concentrate it is the whole question, and nine of the thirteen temperatures we found belong to a concentrate.
One more thing worth recording, because it shows up in other people's comparison tables too. Auto Express ran its own freeze test on screenwash samples and reports Autoglym Ultimate as protecting to -45°C, taking the neat figure. Parkers lists a top pick at -45°C and Prestone at -23°C with no dilution given in either row, while its own general advice says winter calls for a 1:1 or 2:1 mix. Those tables are not wrong about what the makers claim. They are repeating a number that belongs to a dilution their own advice tells you not to use.
Common questions
Can I just use water in the washer bottle?
In summer it will clear a dusty screen after a fashion. In winter it freezes, and a frozen reservoir means the washers provide no fluid. Regulation 34(6) of the Construction and Use Regulations requires washers to be maintained in efficient working order at all times while the vehicle is used on a road, and section 3.5 of the MOT inspection manual records "windscreen washers not working or not providing sufficient fluid to clear the windscreen" as a Major defect. Water also does nothing about the film of salt and diesel that builds up on a motorway windscreen in November.
Is a concentrate cheaper than a ready mixed bottle?
It depends entirely on the dilution you use, which is the point of this page. Prestone Extreme concentrate costs 265.0p a litre used neat and 13.25p a litre if you really do stretch it to 100 litres, against 130.0p a litre for Prestone's own ready mixed winter bottle. So the concentrate is either twice the price or a tenth of the price of the ready mixed, and the deciding factor is a temperature the listing does not give you.
What does "per litre per degree" mean here?
It is the price of one litre of usable fluid divided by the number of degrees below zero the listing claims for that fluid. It answers one narrow question, which is how much each degree of frost protection costs you, and on that question the spread across these six is 9.2 times. It is a way of comparing claims, not a physical prediction: freezing point depression is not linear in concentration, so you cannot read a figure off this to work out what some other dilution would do.
Do screenwash tablets work?
They work in the sense that one tablet plus water gives a fixed, repeatable mix at a stated temperature, which is more than most concentrates offer. The AA pack states 8 tablets for up to 40 litres and effectiveness to -4°C. That -4°C is the limit of what they can do, so treat them as the autumn and spring option rather than the one you rely on in a cold week.
How much does one fill cost?
Washer reservoirs vary by car, so take 4.5 litres as a common size. At each product's coldest stated protection, filling 4.5 litres costs 91p with the AA tablets at -4°C, £4.05 with CarPlan at -4°C, £5.85 with Prestone Ready to Use at -10°C, £11.65 with Rain-X neat at -15°C, £11.93 with Prestone Extreme neat at -23°C and £12.60 with Autoglym at its 1:4 winter mix for -6°C.
Sources
- The Road Vehicles (Construction and Use) Regulations 1986, regulation 34, legislation.gov.uk, read 4 November 2026.
- MOT inspection manual for private passenger and light commercial vehicles, section 3 Visibility, gov.uk, read 4 November 2026.
- Summary of the requirements for windscreen wipers and washers on road vehicles, gov.uk, read 4 November 2026.
- Amazon.co.uk Best Sellers in Automotive, chart positions read 4 November 2026.
- Auto Express, best car screen wash, read 3 November 2026.
- Parkers, best screenwash, read 3 November 2026.
- Product listings read on amazon.co.uk on 4 November 2026: B0B7JG9WL5, B07F21VBVV, B07QX13TXB, B0CCVFJ94Z, B004DEC8L8, B0011DY91G.
Prices were read on amazon.co.uk on 4 November 2026 and change often. The comparison table above the article is a live feed and may not match the prices written in the text. Look Into earns a commission on qualifying purchases made through the Amazon links on this page, at no extra cost to you.