using a jet wash could damage your seals on the van,and if too strong will remove the paint too as its only microns in thickness.i heard last year that wagon drivers were told not to use them on tyres because it damages the rubber by removing vital oils.
------------- the only silly question is the one you do not ask.
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The jet wash we use at work to wash our trucks will push you backwards but it don't damage tyres, It will lift the stick on signage on the cabs tho so we use it sensibly.
I think the jet washes we are talking about here are the small ones you buy for home use. They are no different from using a hose, just dont get the nozzle right into the seams.