Thing about trying to "wash" out an oil/fat based st
Is that often you cannot achieve a high enough level of surfactant/water level that will overcome the natural tendency of fats/oils to be hydrophobic. That is the stain by nature is going to resist water, and if the water/soap or detergent cannot get to the mark fully, it won't break it up to be removed.
Many of us notice this when getting say salad, cooking or any other oil spot on an item of clothing. You put it into the wash and after drying the stain in total and or its shadow still remains. However if you pre-treat the same mark first, it often is gone after washing.
Of particular worry to wool and silk is that the traditional methods of coping with oils/fats in the wash (use of highly alkaline substances) cannot be tolerated.
Sadly (if that is the proper word) many of the better spot removers of past (Energine, Carbona, Aftra, Guardian, etc...) are either gone or have been reformulated. This is just as well as they contained what we know now are some pretty nasty substances (benzene, carbon tetrachloride), but for most small spots, the new stuff should work fine.