A Driving Instructor's Blog


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A 1976 garage fuel price listFinding an absolutely definitive answer to this isn’t easy. In fact, I’ve found it impossible. However, by piecing various things together, it is possible to come up with a plausible explanation.

It seems that it began in the 1930s, in America. At that time, fuel cost as little as 10 cents per gallon, and considering that cars were quite hungry back then, garages realised that by offering fuel at even a tenth of a cent less than a competitor they were likely to draw in more business. That tenth of a cent represented a significant percentage of the price per gallon back then, so the consumer also benefitted significantly.

You have to realise that garages buy in fuel in huge quantities, and it isn’t priced or taxed in round figures. Also, the profit each garage makes from every gallon (or litre) of fuel it sells these days is very small. In the UK, if fuel was advertised at £1 per litre on a forecourt, the garage in question would only make about 2p profit. The remaining 98p pays for duty, VAT, production and transport, and the overheads of the garage.

So, in 1930s America, garages started showing forecourt prices in fractions of a cent to attract business. I’m fairly certain that even back then, if a price was shown as 10⁹/₁₀ cents (they used fractions and not decimals), there would have been people who religiously worked out how much fuel to put in their cars to avoid the inevitable rounding needed when it came to paying. After all, you can’t actually pay 10⁹/₁₀ cents and realise the cost benefit compared to a competitor, but buy 10 gallons and you have a nice round $1.09 and the full discount.

As time passed, the cost of fuel rose. The benefit to the consumer of pricing in fractions became less, but to the people involved in the supply it was still relevant because the tax on fuel ran to three decimal places, and average prices in any given state to four or more when trying to compare individual garage prices. The car owner might be filling up with a measly 10 gallons, but garages and refiners were dealing with thousands and millions of gallons, and the extra decimal places. But this is where marketing took over.

It is well known that the average buyer will see a £4.99 price tag on something in a different light to one which says £5. In a very fuzzy way, one of them is a whole pound cheaper unless the casual buyer stops to think about it. Well, this works with fuel prices, too. A forecourt price of £118.9p is seen as £118p.

In 50s America and later, as prices rose, the marketing benefit of retaining fractional prices took over, and it has been that way ever since (except perhaps for the adoption of decimals instead of straight fractions).

The UK has always charged in fractions, though the £-s-d monetary system did have ½d and ¼d denominations, which meant actually paying the fractional prices was possible. However, even immediately after decimalisation in 1971, non-denominational fractional prices were used. The picture above is the price list on a London forecourt in 1976 (the days of leaded and unleaded petrol), and it clearly shows fractions of 0.1p, 0.5p, and 0.8p being used – only the 0.5p could have actually been tendered, since there was a ½p coin at the time. It’s also interesting to note that garage prices didn’t start being overtly advertised until about the 70s. Up until then, the price was set on the pump dials, and the picture above shows how crude the system was even in 1976 – a time when the price of oil rose from $3 a barrel in 1973 to $12 in 1974 (a result of the 1973 Oil Crisis). Marketing thus became very significant from the 70s onwards, and now every garage has illuminated signs showing the price.

People often argue that the practice of showing prices to a tenth of a penny is some sort of scam. In reality, at its worst it is simply a marketing ploy, and no different to advertising things at £4.99 instead of £5. I mean, when you buy something at either £4.99 or £5, are you actually getting five pounds-worth of value? The answer is only “yes” if you are buying at cost price, because as soon as someone adds value (by processing it) or their profit margin it becomes a question of “how long is a piece of string?” Fuel has value and profit margins added at multiple stages, and I doubt that anyone in the UK knows what the true day-to-day cost price of a litre of fuel should be based on the unrefined crude oil price. In other words, 0.9p (or 0.7p or 0.5p) tacked on the end of something with a price that fluctuates sometimes daily by 1p or 2p (sometimes more) has no objective financial meaning to either the consumer or anyone else involved in the supply chain.

If fuel is advertised at 118.9p per litre, it doesn’t matter if you see it as 118p or 119p, you’ll still be charged at 118.9p equivalent. If another garage is advertising it at 117.9p, then it is 1p cheaper – whether you’re suckered in by the marketing people or not. Only the price difference between garages (or the price change at a single garage) really matters to the consumer.

Another way of looking at it is what that 0.9p actually means. In my car, if I fill up from empty a difference of 0.9p on each litre would equate to about 40p at current prices. However, as I have mentioned before, pumps have to be accurate to between -0.5% and +1%, and that means that I can quite legally be supplied with up to 30p worth less fuel or 55p worth more.

And the bottom line is that even if the tinfoil hat brigade got its way, 118.9p would become 119p – not 118p – and that would mean paying 5p more on a full tank.


MotorwayIt’s about 50 years overdue, but after the recent yes-it-is-no-it-isn’t nonsense, we now know once and for all that from 4 June 2018 learner drivers will be allowed on motorways.

They will only be allowed on with a qualified ADI, and the car they are in must be fitted with dual controls.

It’s worth emphasising that: you cannot go on the motorway with mum, dad, Kyle (who passed before you), or anyone else who hasn’t got a green ADI badge stuck in the window. This means PDIs – trainee driving instructors with pink badges – also cannot take learners on motorways.


Driver Location SignsI originally wrote this back in 2012, but it has had a run of hits lately so I thought I’d update it.

Although the official line suggests otherwise, I’m sure these signs were around long before I became a driving instructor, and their exact purpose was always a bit of a mystery to me.

You’ve probably seen them. You get them mainly on motorways and they consist of a rectangular sign with yellow writing. There is the name of the motorway, a letter (A, B, J, K, L, or M), and a number. On the M1, for example, if you’re heading one way the letter will be ‘B’, whereas heading the other way it will be ‘A’. The numbers change by 0.5 between each sign.

I had guessed that they had something to do with being able to pinpoint precise locations, and that the signs were 500m apart so the number therefore represented a distance in kilometres. I hadn’t seen them explained anywhere, but it wasn’t until I started teaching people to drive – especially on Pass Plus motorway lessons – that I bothered to find out more.  The trigger was a pupil who knew someone who was a paramedic, and who had been told that these signs “marked the distance to the end of the hard shoulder”.

That explanation didn’t make any sense. It was obviously wrong, since the signs appear even when there is no hard shoulder, and the numbers had no connection whatsoever with the end of it when there was.

Part of the difficulty in finding out what they were for was not knowing what they were called. They don’t appear in the current Highway Code, and Googling for “signs with yellow writing on motorways” or something similar didn’t help (certainly not at the time I became interested , anyway). I emailed the local Police traffic department and that was where I discovered they were called Driver Location Signs.

It turns out that they are “new signs on motorways” as of 2008. That still bugs me, because I’m damned sure they’ve been around longer than that, but maybe I’m imagining it. The Highways Agency has confirmed to me that they were “trialled as early as 2003”, but my memory says they were around even in the 90s. But that doesn’t matter.

Wikipedia covers them in more detail. The AA in slightly less detail. And this one is probably the most detailed.

They consist of three lines of text. The top line is the route name (e.g. M1, M6, M25, etc.). The second line is the carriageway identifier, A or B, and in spite of what The AA says they’re not necessarily London-centric (i.e. just think in terms of ‘A’ being the carriageway going in one direction, and ‘B’ the opposite carriageway going the other). If there are parallel but physically separated carriageways, those running with A are labelled ‘C’, and those running with B are labelled ‘D’. The letter ‘J’ denotes a slip road OFF carriageway A, and ‘K’ a slip road ON TO it. The letter ‘L’ is the slip road OFF carriageway B, and ‘M’ is the slip road ON TO it. Other letters can apparently be used at complex junctions. Finally, the third line shows the distance in kilometres from a known point (usually the start of the road), and is called “the chainage”.

The signs can only be a maximum distance of 500m apart, which is what they normally are, but if there is an obstruction they can be 400m or 300m apart (this explains why they don’t all end in 0.5 km). And they CAN be seen on some newer and very long dual carriageways. There’s a lot more to their placement, but this is a basic summary.

The AA likes to have them quoted when people report breakdowns. I have always assumed that they’re most useful to the emergency services.

There is a Highways Agency leaflet which explains them in simple terms, available to download from Greater Manchester Police.

Knowing what they are and how they work – and being able to explain it – is going to be important when we are eventually allowed to take learners on to motorways (in 2018, if that comes to pass).


RobberThis article was originally published in 2013, but it’s been popular recently so I have updated it.

I’ve noticed that sometimes – and I stress sometimes – the petrol pumps at my local garages jump by 1p after I’ve finished filling my car. I usually notice it if I’m trying to put a round number of pounds worth of fuel in – so if I’m aiming for £40.00 I’ll just hit it, and when I get inside the amount payable is £40.01. Looking on the web, other people have noticed it too, and they are putting it down to some sort of scam. But is isn’t.

There is a simple explanation – given here by Leicester County Council Trading Standards. They say:

Q. When I put the petrol nozzle back the meter clocked up one penny when I was not delivering any fuel, is there a fault on the pump?

A. Sometimes the price advances when you close the nozzle and return it to storage. This can be caused by the hose swelling slightly which allows a fractional amount of fuel to pass through the meter. Because of the high price in petrol only a very small amount of fuel is needed for the price display to change by 1 penny therefore this problem is much more prevalent now than it used to be. One penny’s worth of fuel only equates to a very small amount and is well within the permitted tolerances of -0.5% and +1%. However if the price increases by more than 1 penny please let Consumer Direct know on 08454 04 05 06.

Those tolerances mean that for every 1,000mls (litre) of fuel you pump, you can legally get anywhere between 995mls and 1010mls. If fuel costs £1.20 per litre, that means you might get 0.6p less fuel than you paid for, or 1.2p more. On a full tank in a standard car, that works out at up to 24p less or 48p more fuel than you actually paid for, respectively. I stress again that this is perfectly legal, and is due to the reliability and accuracy of the pumps. Coventry Trading Standards explains it this way. As Trading Standards say, it is well within all the legal tolerances.

A tick over of 1p is insignificant within this legally acceptable range.

Most of the time it is perfectly possible to put an exact value of fuel in and it doesn’t click over. In fact, it happened more back in 2013 – when the price of fuel was up around £1.40 a litre – than it does in 2017 (I haven’t noticed it recently). And yet people are still convinced that there’s a small bloke wearing a striped jersey and a mask sitting inside the pump doing it on purpose. It isn’t a scam, and it isn’t deliberate. It’s just a combination of maths and science.

If you’re worried about it, don’t put piddling amounts in your tank – fill the damned thing up once a week instead of putting a tenner in every other day. One penny on a tank full is a lot less significant than it is on each of four lots of £10.00. And it means you won’t keep snarling up the forecourts for the rest of us as you pay for it on one of your bloody Visa cards.

And one more thing – a tip, really. You often find that the nozzle has got well over 1p of fuel sitting in it when you lift it out of the holster – so turn it upside down to drain it into your tank before you pull the trigger. And do the same thing before you put it back. That should be enough to stop all the sleepless nights you’re having over those pesky 1p muggings you reckon you’re getting – you’ll be getting someone else’s fuel for nothing!

It never happens when I put in 20 or 30 litres of fuel, instead of £20 or £30

Actually, it can. But because of the 0.9p or 0.7p they tag on to fuel prices, aiming for a specific price instead of a quantity puts you close to the tick over point, whereas aiming for a round volume probably puts you somewhere half way between two points. Pumping 20L at 119.9p per litre will give a nice round £23.98, whereas £20 works out at 16.6806L of fuel. That 0.6ml is going to get rounded up.

It’s definitely a scam

No it isn’t. Do you really think they designed them with a line in the software that says:

if (ran == 0) then price = price + 0.01;

The 1p is just an occasional rounding up. It is not a scam.


Bill and Ben - Flower Pot MenThis came in via the Google newsfeeds. It seems that Bill Plant driving school went into administration on 27 April 2017. It has since been bought out by Ecodot, which is:

…a specialist in car vehicle preparation and dual control vehicle hire. Our main services are, Dual control vehicle hire, Alloy refurbishment, Porfessional (sic) Valeting services and Body Repairs

I would have used an image above which related directly to Bill Plant, but from past experience I know that they’re a bunch of prima donnas who threaten court action unless you’re saying anything good about them. Of course, such behaviour makes it even more difficult to say anything good about them.

The reason for the titsup is given as being due to:

…exceptional costs associated with a change in operating model.

Or, in other words, they were a bunch of incompetent prima donnas. Most of the other belly-ups in the driver training industry went bust during the economic downturn during the last decade and the early part of this one. Bill Plant has managed it during a period of economic growth, and that doesn’t bode well for their future.

This industry is not high-margin. Driving lessons can only cost so much before learners won’t pay for them, and at the moment almost everyone is charging the same (in the region of £25 an hour, give or take a few quid). Similarly, instructors who work on a franchise will only pay so much before they walk away, too. The amount they pay for the franchise lines the pockets of the franchiser, who is at the top of the pile, and that franchiser will not be happy unless he or she is pocketing enough to keep a new X5 on the driveway. A kind of status quo is established, whereby the only loser is the instructor – lesson prices can’t go up by much, and the franchiser will still want to increase profits year on year, so the franchise fee goes up. It’s a simple Law of Nature.

It makes you wonder what the numpties did to their “operating model” to screw things so badly. I wonder if it had anything to do with introducing BMW X1s as tuition cars – the prices of which range from £23,000 to £35,000, which is at least double (and up to five times) the price new of most instructors’ tuition vehicles? If it did, I can’t see Ecodot – which is apparently now trading as Bill Plant Driving School Ltd – keeping them. Someone somewhere in the chain has to pay for the overheads.

As I say, this industry is not high-margin, and anyone who buys a top marque as an overhead and then delivers lessons costing the same as they would in a vehicle costing a quarter of that is not going to stay in business long without someone on the outside pumping them money intravenously. Having hubby (or wifey) supply the financial drip feed to their other half is one thing, but for a limited company it’s a different matter altogether.

Ecodot isn’t big enough to pump money in indefinitely, and I can see big changes coming.


Bus LaneThis BBC story reports that bus lane enforcement cameras make £31m per year in fines. One particular lane, in Newcastle, made £1.5m on its own – and that’s after you consider that the BBC contacted 160 local authorities for financial data.

The fun part is where a spokeswoman for Newcastle said:

We would firmly stress that bus lanes are not there to generate income – they are there to help us to manage our road networks efficiently.

Liar. Bus lanes CAUSE congestion, and they have done so since the day the first one was introduced. You have to be a complete idiot (or pathological liar) either not to realise that, or to argue the point. So sticking cameras on them can only be to make easy money.

A prime example in Nottingham is the A52 Derby Road heading into the city via the Priory Roundabout. It used to be three lanes in merging to a single lane going out, past Wollaton Park. There was always serious congestion during rush hour. Then, they turned the left lane into a 24-hour bus lane, and suddenly three lanes of traffic was forced into just two, with still just a single lane leading out. The only benefit was to buses, which were now able to skip about three-quarters of a mile of gridlock and force their way back in at the roundabout (“force” being the operative word when Barton, Indigo, or YourBus are involved). Since much of the congestion was caused by buses stopping for extended periods of time on the single lane side (all the stops are next to the University, and you can imagine the difficulty most students are likely to have getting on a bus), having them all get down there more quickly made the congestion even worse. Admittedly, it doesn’t have cameras on it, but there are plenty that do.


Ford Focus oil change messageI got a message on my 2016 Ford Focus TDCi Titanium centre console the other day telling me that it was due for an oil change. I wouldn’t have minded, except that it was only on 5,500 miles and service points are every 12,500 miles.

I spoke with the local dealer and they said just to bring it in so they could reset it. I wasn’t too pleased with that since visits to the dealer inevitably mean at least half a day in lost lesson time. Therefore, my first action after that was to buy an OBD II monitor tool so I could reset it myself. The tool worked fine, except that it didn’t find any faults and so there was nothing to reset – and the oil change warning remained stubbornly visible.

Then I did what I should have done in the first place and Googled it. It turns out Ford has a system which can be set to give an oil change warning at various points, so when it triggers it isn’t an actual fault and therefore doesn’t show up as one.

How to reset the warning

Resetting it turned out to be incredibly simple – though completely undocumented by Ford, of course. All you do is:

  1. Turn on the ignition (or push the start button with the clutch up)
  2. Press the brake and accelerator fully down for about 20-25 seconds

The display tells you when reset is complete, and the warning goes away. From what I understand, this applies to all Focus models from MkII onwards.

How soon should I get my oil changed when the warning message comes on?

For a Focus, if your car is under the manufacturer’s warranty then I think they allow 1,000 miles on top of the normal service points at every 12,500 miles. After that your warranty might be affected.

Of course, if the oil change warning message appears before 12,500 miles then you can safely ignore it (or reset it, as explained above). It isn’t a sensor warning, just a timer based one.

If the oil warning dashboard light comes on, though, you mustn’t ignore it.


MotorwayActually, it’s only a small section of the M1 – near Sheffield – but the media likes to distort these things.

I wrote about this subject a few years ago. That was at a time where they had only recently been talking about raising the speed limit! My main point was that although cars emit less pollution when driven at 60mph instead of 70mph, they they take longer to pass through a given area at 60mph, so the reduction in pollution is pretty much negligible. It’s a case of comparing a quick but pungent fart with a longer, less smelly one.

The other thing I think I mentioned is the stench when you drive on the M1 past Sheffield and the wind is in the right direction. And it doesn’t come from cars – it’s from the factories around there, and a smell like that isn’t going to contain anything that is good for you.

An even greater irony this time around is that London is currently in the grip of an extremely poor period of air quality. They haven’t quite got round to blaming it on cars and lorries yet – that’s been done before – but at the moment the most direct blame has been placed at the feet of pretentious people burning wood during the cold weather (though that detail seems to have been removed from some reports).


Over the years, I have updated this article several times as I have found progressively better solutions to the problem. I’ve now found pretty much the complete solution.

The problem of smeared windscreens in the rain has been driving me nuts ever since I started driving, but it became a major headache once I started teaching people to drive.Smearing windscreen in rain

I guess everyone has experienced it. You get a few spots of rain, and when the wipers wipe you get a mosaic pattern left behind for a few seconds. But in heavy rain it’s like someone poured chip fat on the screen and you just can’t see properly. I’ve had varying levels of success removing it – scrunched up newspaper (no good), sodium lauryl sulphate (not bad), various solvents (fair), Clearalex (quite good) – but things came to a head when my lease company replaced my last car. In rain you couldn’t see anything, and absolutely nothing would get rid of whatever it was on the windscreen. I was close to assuming that the glass must have been damaged in some way since it was a brand new car.

Where does it come from?

In normal circumstances, every vehicle that uses our roads leaves deposits behind. Some of it is dusty, some is gritty – but a lot of it is oily. That’s why when it rains after a period of dry weather we’re advised to take care, because the road can be very slippery as water and oil sit on top of the tarmac before the oil is eventually washed away. While it is fresh, road spray is obviously going to be a mixture of dirt, oil, and water, and when this gets on to your windscreen you start to get smears. Now, up to a point, your screen wash can deal with it (unless you just put water in your tank, in which case you’ll get smears all the time). Eventually, though, the oil seems to bond to the screen such that removing it is no longer easy.

Another source of windscreen contamination is, oddly enough, washing your car. Even if you don’t choose the waxing option in the car wash, the brushes will be contaminated with wax from people who did, and if you’ve ever noticed how a single fingerprint can be smeared across almost a whole mirror or windscreen unless you use something which lifts it off, you’ll realise that a little wax (or oil/grease) can go a very long way. Even if you hand wash your car, small amounts of wax and oil gets on to your rags and gets spread on the glass. It also gets on to the rubber of your wipers, so it is smeared back on as soon as you use them, even if you got it off the glass. People often forget that the wax (and oil) collects below the wipers, and if you don’t clean that area properly, the wipers dip into it like a pen dipped into ink and spread it across the glass again.

The particular problem with my lease car turned out to be the result of a manufacturing residue as far as I can tell. It’s something that gets on the glass during manufacture, and which they don’t remove properly.

How can you get it off?

Most detergents and surfactants will remove the normal deposits of wax and oil with varying degrees of success, though car wax is particularly stubborn. Even Fairy Liquid works up to a point. Some cleaners are more powerful and are much more effective. You used to be able to buy powdered products like Clearalex in sachets (they sell it in liquid form instead, now), which you add to your windscreen washer fluid. Clearalex works quite well, but leaves terrible white residues when it dries (which I find very distracting). I have also had some success with Sodium Lauryl Sulphate (SLS), which is an anionic surfactant used in many household products. SLS removes quite a lot of windscreen gunk, but it won’t touch wax and it leaves a slight residue when used at the required concentrations. I was very happy with SLS until my recent vehicle change, where I found that no matter how much I used it would not touch whatever was on the glass.

After a lot of research, I found a reference to sugar soap. I’d not heard about this before, but it is used by decorators and builders to remove grease and dirt from surfaces prior to painting. Sugar Soap - from Screwfix

Wikipedia describes it thus:

Sugar soap as typically found in Commonwealth countries is a cleaning material of variable composition sold for use on surfaces affected by greasy or tarry deposits which are not easily removed with routine domestic cleaning materials. When in dry powder form it looks like table sugar thus causing the name.

The solution is alkaline and its uses include cleaning paintwork in preparation for repainting.

It looks like Clearalex powder, and I suspect that there may be some similarities in chemical composition. However, sugar soap is dirt cheap, at about £2 for nearly half a kilo from Screwfix. I bought some, made up a batch using information on the pack, and gave the windscreen a good scrub using it. I rinsed it and took the car out for a run in the rain.

Initially, I didn’t see any difference, but after a few wiper passes the glass was getting noticeably clearer. The sugar soap appeared to have softened whatever it was on the glass and it was gradually coming off. So when I got back home I made up another batch and soaked some rags in it, then left them covering the windscreen (including the bit at the bottom) for about half an hour. I also cleaned the blades with it. This time the windscreen was absolutely crystal clear.

Sugar soap is great for one-off cleaning, but being a solid there is still the problem of residues if you use it in your normal washer fluid.

A while later, I started using a local hand car wash. I was intrigued by how easily they managed to remove every trace of dirt and oil from the car with only a power spray and some mysterious hand-pumped spray guns with various liquids in them, so while they were working I did a bit of snooping and noted the names on the various drums and containers lying around. The important one turned out to be “TFR” – which I discovered means “traffic film remover”. Already this was sounding quite exciting (well, it’s exciting if you’re a chemist) due to theory behind the way TFRs operate.

I bought some TFR from a company called JennyChem. They also supply the mysterious cherry-smelling shampoo the hand car washes use. In a nutshell, a 1-2% TFR solution gets all the oil/wax film off a windscreen in one go, and it seems to also attack the residue I’d been plagued with on my lease cars (I’m getting a new one soon, so I’ll test this out properly then). The same concentration in your wash bottle keeps it off. I use a combination of sugar soap (soaking using rags) and TFR as required, and a 1% solution of TFR in 10% ethanol/water as my screen wash. I also use this solution in a hand spray bottle for spur-of-the-moment cleaning, and for doing the inside window surfaces.

As time has gone by, I have started using the TFR spray to clean my alloys and bodywork in between visits to the hand car wash when I have an upcoming test. It removes brake dust from alloys like all get out, as well as summer tree gum and bird crap (especially when the little sods have been eating blackberries and insist on sitting on the telephone wire right above my driveway).

I’m getting a lot of hits on this now I’ve mentioned TFR.

As a footnote, my hand car wash has just started using what I am assuming is a liquid wax (I haven’t yet identified it) that makes water bead very easily (and very impressively) when it rains. The problem is that it gets on the windscreen, and it is a sod to get off (two sugar soap treatments did it).

Does TFR damage the windscreen?


Does TFR damage paintwork?

If it is the non-caustic type, and if it is used at the manufacturer’s recommended concentration, no. But remember that TFR will remove any wax you have applied, so you will need to re-wax  after using it on painted surfaces. However, removing wax is exactly what you want if it’s on your windows.

Strongly caustic types – which are cheaper and harsher, and often used to shift several centimetres of crap off the undersides of lorries – could damage painted surfaces if used at high strengths and if left on for too long.

The stuff supplied by JennyChem (linked to earlier) is not strongly caustic as far as I am aware, and is specifically designed for use on cars.

Does TFR leave a residue?

The stuff I use doesn’t – well, no more than normal windscreen washer solution does. You’ve got to remember that when you use your windscreen washers, you’re doing it to remove dirt on the windscreen. That dirt is visible, so when you wash it off it will leave visible streaks outside the wiper area when it dries. It’s like when a bird drops a load on the screen – when you wipe it off there’s a good chance it will sit on the screen at the edge until you scrape it off by hand. There’s not much you can do about that.

Is there a non-chemical solution?

A reader (from Australia) wrote to me recently to tell me that he had had success removing that new-windscreen film using Cerium Oxide paste. You can buy it easily from various places (including Amazon) in various forms – powder, paste, or block – and it is specifically used for polishing glass. If you buy it, make sure you get the finest grade possible – ideally, one which is specifically sold for the intended purpose.

Can you put oil on the windscreen to prevent smearing?

Or, as it was put to find the blog, “can u put oil on wind screen 2 prfent rain”? NO. It will make it worse. It’s oil (and suchlike) you are trying to remove. Put it on deliberately and you could end up killing yourself – you won’t be able to see properly.

You can buy things like Rain-X, which are intended to make water bead up and roll off more easily, but those who use it often complain that it is patchy in coverage and leads to worse problems with smearing when the wipers pass over the glass, especially as it starts to wear off. I nearly tried this, once, but the risk of it causing more problems put me off. I’m not saying it doesn’t work, just that not all reports about it are as positive as the advertising is.

My windscreen is smearing when it snows

That’s probably a different thing, and not “smearing” at all.

When the windscreen wiper rubbers get cold, they also get stiff. As a result, instead of flexing to the windscreen contours and bending forwards an backwards on each stroke of the wiper, they snag and bounce across. They may even not touch parts of the screen properly on the wipe. All of this is often accompanied by a horrible grunting sound, and it leaves behind a trail of smeared water.

Also, if there are remnants of snow on the blades, this can leave a trail of melt water as the blades wipe.

There’s not much you can do if it’s really cold except put up with it, or let them warm up as the windscreen warms up. But scrape off any snow or ice and at least you won’t get melt water (and they’ll warm up quicker if they’re going to).

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