''Oil-impregnated'' is not the same as ''... in Oil''
In our documents + brochures, some capacitor types are described as "oil-impregnated", which is often confused with "Xyz in oil". As a result, users who, for whatever reason, have an open "oil-impregnated" Mundorf capacitor in front of them, are irritated because they see no oil (flowing) and therefore suspect that something is not in order. However, everything is fine, since only very little oil is required for ‘oil-impregnation’: The oil is sucked into the finished capacitor-wounding by means of negative pressure (vacuum), and only distributed as a ‘wafer-thin’ but tightly pressed oil-layer between the metallized polypropylene winding layers (analog to ‘baking’ coils) for to prevent even the windings’ slightest vibration. You can smell the oil slightly when you open the capacitor, you might feel it, too, but you certainly won’t see it flow when you unwind the coil. How little oil is really used in our "oil-impregnated" capacitors - and we don’t have any other oil-involving capacitor type - is shown in the below photographs.