Why bother cleaning the boards at all? It is only for cosmetic effect, it does not make any difference to the reliability of the boards in the long term. In fact you could argue that boards that have not been cleaned are more reliable due to the fact that the components on the board have not been subject to what ever solvents you have used. Fluxes used should be PH neutral and should not promote fungus growth. You can get fluxes that leave no visible residue.
One of the main problem I would imagine with cleaning boards with petrol is that it would leave a smell that would take a very long time to go (if ever)
There is no such thing as a no clean board, for ultimate reliability you have to clean your boards....
As to using petrol.... IPA or an aqueous based cleaner is best.
More info, there is a lot out there.
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