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What's the cheapest way to wash a car?

  • You'd think the car would wash by itself in the rain, but it always appears dirtier after it rains than just before the rain.

  • One may think that washing the car with the paper towel at a gas station is a possibility, but the raw amount of dirt always ensures that stains will remain everywhere (if you don't even ran out of paper towels long before any sign of finish).

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    Don't ever use paper towels to wash your car. It is a very abrasive material and without the proper lubricant (soap), your paint will have swirls and clear coat scratches. – Flat Banana Mar 6 '17 at 15:05
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Once dirt has attached itself to the car's surfaces, rain often isn't enough to dislodge it. You need soap of some sort. This will attract the dirt particles and encapsulate them so you can rinse them off.

Among the larger dirt particles you can find e.g. sand and other abrasives. This makes it important not to smear the dirt around, because that way you'll scratch the paint.

Rain isn't clean water. Raindrops form around small particles of dirt. In areas with a lot of air pollution, falling rain will pick up more dirt.
Rain that hits the pavement will spatter, transferring more dirt from the pavement to the car.

So rain is useful to get the car wet, but then it's time for a bucket of clean water and soap to get the dirt off. Use lots of water to rinse the car, getting the dirt off without having to touch it.

The cost of a sponge and some soap is very small (in the region of €5 gets you enough material for a year's worth of washing your car). If that's too expensive for you, not washing the car is better than using paper towels.

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    In addition to @Hobbes advice, I would add CAR WAX. If you apply wax to your car, it will repel dirt better, protect the finish and water will bead up and roll off keeping your car cleaner than an unwaxed vehicle. You can buy a small container which will last many waxes for a few dollars, or most self-service carwashes, sell single-use car washing items, e.g. wash liquid, micro-cloths, car wax for very little cost. – M.Mat Mar 12 '17 at 2:40
  • I don't really buy the excuse that the soap will somehow make the dirt less abrasive to the car. Is there any science behind it? I did the procedure described in my own answer, and never had any issues with it, unless I tried doing it after the rain has already finished. – cnst Jul 24 '18 at 19:21
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I found that the best way to wash a car for nearly free nearly anywhere is the following set of steps:

  1. Wait until it starts raining and the car gets wet.

  2. Ensure it'll still be raining for a while.

  3. Find a moment when it's either not raining too much (just before another storm wave hits), or find a cover such as to allow yourself to be outside for a few minutes, but without getting too wet (e.g., a garage, either public or private, or a covered petrol station).

  4. Get a paper towel, and gently break the film of dirt that forms a dirt barrier on the car, getting dirt all over the car; you'll see why we refer to it as film as you start doing it; don't worry about the excess dirt, as long as the dirt film gets broken for good, and the rain hasn't finished yet.

    As you go with the paper towel on the wet car, you'll notice how the film of dirt get broken up, forming individual spots of very dirty water droplets (which the rain will have no trouble dealing with, unlike the thick film of dirt); make sure to cover all of the car as such; changing paper towels, nor rinsing them, is not required.

  5. Get the car back into the rain ASAP. Ensure that after breaking the dirt film, the dirt never dries up, prior to being washed away by a decent rainfall (otherwise, the car will have lots of dirt stains).

I've used the method multiple times, and, when used correctly (e.g., you ensure the rain will remain for the rinse), it has great results, and the car gets sparking clean; with no tools required.

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    Rub grit all around to scratch the paint. – paparazzo Mar 6 '17 at 9:46
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Don't do anything.

Rain isn't clean. It has dissolved dust inside each drop. When the rain dries, that dust will be left on the car, in the form of water spots. You can scrub your car all you want, but there will still be water spots if it continues to rain. Unless there is dirt caked on your car, a soapy rag is what actually cleans the car. Water running over the surface of your car will not clean the car. Your best bet is to wait until the rain stops, and wash it with a microfiber rag (a couple dollars at most) and some dish soap. Hose it off, and dry it with a clean microfiber rag.

If you insist on washing your car in the rain, you'll need a soap to attract the dirt. Otherwise, the dirt will remain stuck to the surface of the paint (and will remain in the microscopic scratches in the paint). Get a clean microfiber rag, and put a little soap on it. Wash the car with the rag, and then hose it off (rain doesn't provide enough volume of water to rinse the soap off). Dry it off once the rain stops, before the car has enough time to air dry. If you let the car air dry, there WILL be water spots.

If you are washing your car in the rain because you don't have access to a hose, try some waterless soaps made specifically for washing vehicles. They aren't very expensive, and they will certainly do better than trying to wash your car in the rain.

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I will always suggest to keep thin cloth/fabric made from cotton or wool in car.While your car is still wet just put on the cloth totaly flat and pull over it slowly by your side. Water drops will be absorbed by fabric and pulling it slowly over your car will clean the surface.

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The best way to wash your car for free at the gas station is to use the window-washer squeegee that most stations have available next to the pump. These usually have a spongy side and a rubber side, and there's usually diluted soap in the water provided for the squeegee.

Use it just like you would on the windshield: spongy side to loosen up the dirt, and the rubber side to wipe it off. Be gentle with the rubber side so that you don't scratch the paint. When this is finished, gently blot up excess water and dirt with the paper towels.

People will give you funny looks, but if you're doing this to save money, who cares?

  • Absolutely not! This is like the worst possible way. Have you ever tried it yourself? Your car will only get dirtier, especially given how "clean" the water at most gas stations is. – cnst Aug 2 '17 at 21:25
  • @cnst I washed my car this way a few times in college. Have you ever used the squeegee thing on your window? It makes it cleaner, not dirtier. The only way this could possibly make your car dirtier is if you were dunking the squeegee in mud instead of the soap-water. – user45623 Aug 2 '17 at 23:59
  • I guess it may be fine in the end — they don't really put too much soap in those things — but I'd be concerned about leaving the soap designed for windows onto the paint of my car. – cnst Aug 3 '17 at 0:10
  • At many gas stations, that bucket is filled with fresh water maybe once a day. So after a few uses it'll be quite dirty. There's also no detergent in it, usually. And the squeegee is going to be dirty too. So this is about the worst source for fresh water you can find. – Hobbes Aug 21 '17 at 9:37
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Use dish soap like Dawn (no additives added such as fragrance and skin conditioner) and a scratch free brush (or better— a soft sponge to gently agitate the grime. ...absolutely the cheapest tools that do a good job.

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