Could be watermarks or grime mixed with fusso.

prolonged stains on white car wont be easily washed. Use a decent car polish should help. Dont bother those cheap one from DIY , tried before didnt work.
you send to petrol station car wash and upgrade to WAX wash rm30 , they will remove. Theirs are some powerful detergent not caring much on paint protection.

white car 1 week also prolonged
but your case, basement parking must be from leaking ceiling or pipe toxic stains

cant see the stains in your photo.

The stains seems to come from just normal everyday grime mixed with rain water. - if this may means water mark caused by rain water, do you see little circle marks when view at an angle or with light refection?

if worry go for a good polish/wax to clean off your paint condition. then observe if it reoccurs.

sounds awfully similar to what i used to have on my Taffeta White Accord - no amount of washes can get rid of them but if you take a clay bar to it, you'll notice that they lift right off. i still cannot find the cause for it except to assume that it was the (coincidentally) Fusso Coat 12 Months Wax Light Color that i used and that the road grime somehow bonds to it.

other than that variable, i cannot think of anything else and unfortunately (or fortunately) i didn't kept that car long enough to ascertain whether it was the wax or not. however you can try for yourself and see.

if the stains can be removed via a claybar then you remove a small portion of it but enough to make 2 parts, one being the part without the wax and the other with the wax applied. leave it for 3 to 5 months and then see the difference.

the liquid should be some sort of cleaner (IPA or alkaline based solution) which generally would remove most stains but at the same time strip almost all LSP on car paints so if you pour water over the part that has been wiped, you should notice that water no longer beads and also it sheets on it.

with ceramic coatings now becoming very affordable, it is a good long term investment for your car. all other superficial claims aside but it definitely makes car washes a heck a lot less tedious.

not sure if you are using the same product as me but this is what i had:-



the most common one would be ceramic, there are some shops advertising "graphene" but it is uncommon and the difference in results between the former and the latter are arguable and the downside, you will be charged a premium for that with little to prove.

Saw this ad at my fb also lol
That price for 5 year mcm doggy, try ask maint period and price lol

I have patches of stains everywhere on my car after didnt wash my car for 2 weeks. Normal car shampoo wont clean it off. I took it to my detailer and he cleans it with some liquid - wont tell me what it is though.

This is a one year old car. Always parked under basement. The stains seems to come from just normal everyday grime mixed with rain water. Never experience this before in other cars.
Any idea how to clean this myself? Or should I do some ceramic coating ? Oh btw the I applied Fusso Coat on it and wash with the cheap soft99 shampoo. Usually I wash every week and the stains wont appear but if I leave it too long then these stains will set in

I just use this, spray let it sit for 1 min, buff and rinse kaotim without killing the coating.

https://my.shp.ee/zvMDT8k

Sorry to bump a reply from so long ago. I believe what you had is road grime/dirt bonded to your paint/sealant, unfortunately it’s very obvious on light coloured cars, not restricted to white cars only.

From your photo looked like there were some high and low spots of the Fusso coat since it does not appear exactly like normal watermarks etching. I had similar issue before with some wax as well, got most of it out by using a clay bar. Removing it by polishing works too, but may not be the best method as one should always start with least aggressive method. Some may argue must polish after claying since that install swirls and marring too, depends on the assessment of the detailer, ymmv.

There are quite a few “ceramic” sealants or sprays that can last 1-2 months easily and have comparable water beading behaviour like fusso coat in the market now. Perhaps you can try, and can’t avoid routine wash for light coloured cars, it’s a lifestyle