What it says it does
The claims are "Repels rain and reduced the adhesion of sleet and snow. Improves visibility"

Thats about all it says, the picture on the bottle shows half a window without rainx all water logged and you cant see, the other side with rain x... WOW its clear, this stuff looks like magic. Time for me to give it a try on the front and back.

Application
Better do this right, fully cleaned the car, cleaned front and back windows with Auto Glym Fast Glass, let it dry then applied the RainX exactly how it says on the bottle. Just take a clean cloth and wipe it on in overlapping circular motions, let it dry and buff off.

I applied to the front window and the back.

How it works
Some polymer thingy, basically its like a clear wax for glass, makes water just bounce off

Results
The main reason i tried this stuff was for the back window, with no wiper and the rainy winter months upon us i can never see out of it in the morning. Its not until you get going that the window clears. Now one thing to mention, how well this stuff works depends on the rain size, your speed and the angle of your glass!! so the results vary from car to car.

Lets start with the back window. Stuff on, polished off and the next morning a window full of water, cant see a thing. Drove off and nothing, still couldnt see. Its not until i got to 40mph or faster that the water did just run off. Nice and clear within moments but you do have to be going 40 or over :S hmmm, not what i was hoping.

Now for the front window. Its rained a bit here now, big rain, small rain and mist. all the usual stuff for the UK.

With mist and doing 70mph down the motorway this stuff didnt do much. Yes sure the water rolled off eventually but not fast enough to be of any use, so on go the wipers.

Few days later, some bigger rain, 70mph down the motorway again and yes, the water rolls off but not fast enough to make your vision clearer. Back on with the wipers.

Only one problem, since applying this stuff if i do have to use the wipers I get a very streaky window. Its actually harder to see now when it does rain.

While it does what it says, rain rolls off but it dosnt do it quick enough, even at 100mph it just dosnt clear fast enough to make the wipers redundant.

I would deffinatly recommend it for the rear window but for the front, its best without it IMHO

UPDATE
Using your wipers
Yes you can use this stuff but NO!! you cannot stop using your wipers. While this stuff is ok at having the rain run off what about mud, dirt and.... ROAD SALT!

Its winter here now and every day im having to swoosh my screen to clear the road salt and this is where the problems begin.

My screen wash is a normal winter concentrate of water and antifreeze. Unfortunatly this stuff has detergents in which means the water dosnt form droplets, the surface tension is weakend by the detergents. This means rainx is now... useless. So when I swipe the screen rainx is trying to do its thing but just ends up leaving me with a very smeary screen. Now my driving is more dangerous. Also, the detergents are slowly removing the rainx and after just 3 weeks i have to go 80mph to start having run off... 80MPH!!!!!!

I find it smears the screen when you have to use the wipers, e.g. driving around town so I stopped using it.

i AGREE GREAT ON THE BACK WINDOW AND THE WING MIRRORS BUT ON THE FRONT IT JUST SMEARS AS SOON AS YOU PUT ON THE WIPERS

I used it on my last car but found it pretty useles especially on the windscreen and after cleaning the car I found it difficult to get the windows dry. I would not use it again.

RainX is great! But you have to control yourself NOT to use the wipers. The drops will fly away from 40mph on. If you have to drive long distances on higher speeds it is a very good plus in safety (If you get ahead of a lorry while heavy rain for example). You won't need wipers for about 4 Weeks . Then it's gone.

If you only drive innercity it is useless.

And if it is wet outside and the sun is shining the sunlight will spread within the front windows. This is bad but not very common and no problem if you know it.

Please don't use the wipers after finishing the screen with RainX! Golden rule!
Use the wipers only if you don't have an alternative.

I used to love it but now I find its got too many drawbacks. You have to go over 40 mph everywhere which is harder than it used to be because of the traffic.

If you're behind a lorry and you get mud splatters on your windscreen you have to use the wipers and that rubs off the rain-x. To counter this you can put some rain-x washer additive in your washer bottle. On the whole I think it's expensive for what it is and when this batch i've got runs out i'll stop using it.

I think its pretty good. don't need to use wipers above 40 ish mph. only problem is you've gotta keep putting it on every nown and again

Thanks for the review mercenary, I now know not to bother!

Rain wizard is an alternative.
Better than Rain X, but still don't use it on the windscreen.

Rain-X is great on motorcycle helmet visors. Just turn my head slightly to one side and..........woosh the rain's gone. You must resist the temptation to touch it (or use your wipers).

I wouldn't use it on the windscreen of my IS but sides and rear are fine.

Has anybody actually tried to fit a wiper of some description to the rear window? I'm sure with a roof spoiler and a wipe from a hatchback (or RX300) something could be done. I could fit it but not fabricate it. Something for Mr Prolex to look into?

Mike

deffinatly on the back, it helps. But the front. best without it.

I got some (mainly for the back windscreen)and tried it on the front windscreen and wish I never.smear city!!!well advised to put on rear windscreen but steer clear of the front

You have a rain wiper on your helmet ? coooooooooool !

if he did id imagine it would be like those comedy glasses with wipers on

Fwiw, I've used Rain-X for several years on the front windscreen - and used wipers & screenwash - with no real problems. At low speeds (below 40 mph) the rain "beads" and, although it stays on the screen, it causes less obscured vision than without it. At higher speeds the wind drives the rain off quite well. Wipers are still needed for best visibility, but the benefit is worth it.

Yes, road crud (diesel, oil, salt, etc) will cause it to 'break down' and the more you drive, the more often you'll need to re-apply it (up to once a month in winter), but even so, it's far better than not using it.

Spider

rain x is brilliant if you can drive at a constant 80mph in the wet and it does do the job its supposed too its just no good at low speeds

Strange - I use it on my screen and have no smearing issues.
Have you put it on / buff off / sprayed it and re-polished it - this seems to make it last longer and not smear ...
Does make it harder work to put on though.

I agree - I have been using RainX for about 10 years now on a range of cars - its one of the first things I do when I get a car.

It is one of the best car products ever. Just keep on building the layer up on the windows, just like wax. Remember and after first application use a spray of water to wipe off and reapply.

I have never had it smear. It can be quite hard work though