An hydraulically set oil-permeable cement body is provided in the form of a stand-alone block or briquette for preserving cooking oil during deep fat frying, said body. It has substantially no free water or having a low free water content for resisting damage on immersion in cooking oil and initial heating and is enclosed in packaging that resists ingress of water or water vapor The block or briquette consists of >50 wt % of a mixture of milled white OPC clinker and white OPC, optionally silica 1-2 wt % and/or titania (TiO2) 1-2 wt % and optionally further ingredients selected from calcium silicate, magnesium silicate, aluminum silicate, natural feldspars, natural sodium zeolites, natural calcium zeolites, synthetic sodium zeolites, synthetic calcium zeolites, wollastonite, calcium hydroxide, clays, pillared clays, activated clays/earths, talcs/kaolinite, amphiboles, granite porphyry, rhyolite, agalmatolite, porphyry, attapulgite and diatomaceous earth. It has the properties that calcium and magnesium substantially do not leach into the oil and that it is porous so that oil can diffuse into it and contaminants can be deposited on and within it.