Filter was blocked, we took the filter off the van Blocked up one end and poured two bottles of the cleaner in then stood it on its end to soak, after an hour the cleaner still hand not made its way through the filter.
We eventually cut the filter in half and using a combination of thinners and a steam cleaner cleared the filter, welded it back together and re-fitted it to the vehicle.
This product may work on a lightly blocked filter but on a heavily contaminated one I think its a waste of time and money.