Detecting hydrocarbon fuels in lubrication oils

A system comprising:

• a pipe defining a first inner bore configured to flow a lubrication oil;
• a housing coupled to the pipe, the housing defining a second inner bore and a cross-sectional slot, the second inner bore of the housing aligned with the first inner bore of the pipe for flow of the lubrication oil;
• a fuel detection film disposed within the cross-sectional slot of the housing, the fuel detection film spanning across the second inner bore of the housing, the fuel detection film comprising a cyclic olefin copolymer that is insoluble in acyclic saturated hydrocarbons, the fuel detection film having a porous structure defining a plurality of pores configured to allow flow of the lubrication oil through the fuel detection film via the plurality of pores, the fuel detection film is configured to at least partially dissolve in a presence of an aromatic hydrocarbon in the lubrication oil flowing through the fuel detection film;
• and
• a multimeter coupled to the fuel detection film at two locations on the fuel detection film, the multimeter configured to apply a current across the fuel detection film, the multimeter configured to measure a resistance of the fuel detection film at least based on a voltage drop exhibited by the current applied across the fuel detection film, wherein a change in the resistance of the fuel detection film indicates at least partial dissolution of the fuel detection film and the presence of the aromatic hydrocarbon in the lubrication oil.