I have noticed in the Purolator cross reference book where you look up to find the part # for your car that the 20033 Pure One filter has a note reference next to the Pure One number and when you look at the footnote's for that note reference, it says that that filter has been discontinued...Not all the PureOne filters have that reference, so it seems to me that they are discontinuing certain applications...
Just about everytime I go into Advance Auto, I grab both filters that are usually on the shelf and buy them, whether I need them at that time or not...I think I get them for around $5-$5.50/filter...They never have more than 2 in stock...