I solved this problem in minimalist way - I wash my car maybe twice a year. It sits in my driveway in rain anyway because my garage is waiting for some spare time so that I can finally reuse all that pallets I collected since last year (mostly clean pallets I've already made some nice yard furniture for myself and family, all those pallets already have planned use but I don't have enough time).

They said "Even if you use environmentally friendly soap, or no soap, the water coming of the car isn't exactly clean."

If the rain is falling on your car it will have the same issue, no?

Not really something you can reasonably address.

I disagree, you can address it by keeping your car cleaned regularly at a car washing business that filters and recycles wash water.

Meh, there's a big gap in your problem/solution - driving in rain.

If you're cleaning it regularly then the rain won't wash off very many pollutants.

Pallets are often treated with chemicals, so keep that in mind.

That's why I wrote that they are clean, I keep that in mind, but thanks for noticing.

You said "mostly clean" and I assumed that this was about dirt and debris, and the stuff they're treated with is not visible. There is a stamp on the side which shows how they have been treated, though.

True but it's very much not all pallets. EUR pallets are mostly heat treated. Some are methyl bromide fumigated but that is banned in Germany.

Twice a year! How decadent!

If you have a whole half ton of energy guzzling metal machine just to move you around town, are you minimalist?

For moving around town i just walk, maybe sometimes I use my 20yr old bike. My car is used only to travel from my town to nearest city, because it takes 3x more time to go with bus->train->taxi to where I need to go and is a little more expensive. Then it sits idle 5 days. It's more like 1.2tons and is not that guzzling, 7L/100km. Diesel or hybrid would be guzzling even less, but they break more and/or are more expensive. I'm not a eco freak, I do what I can, but some people really do need to own some transport. In Poland, if I see someone with a big pickup, it typically means he actually DO uses it to pick up various things otherwise it would be too inconvenient to own such a big car.

Yup, I worked at a car wash and the water coming off of cars is absolutely disgusting. Had to wear some sort of hazmat type suit to clean the trench as we called it.