A method is provided for preserving cooking oil which may be cold or heated or during frying operations, which comprises in situ treatment of the oil withal least one oil-permeable cement body which has been hydraulically hardened from a paste comprising cement clinker and cement e.g. white OPC clinker and white OPC. The invention further comprises cooking oil having therein at least one oil-permeable cement body which has been hydraulically hardened from a paste comprising cement clinker and cement and an oil-permeable cement body for use in the above method.