First of all, you should try to find out what kind of oil it is and out where it comes.
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First of all, you should try to find out what kind of oil it is and out where it comes. May be it is not an oil, but it's antifreeze, if it's oil first you have big troubles with your engine, also it can be oiled from the car's gearbox. If it's antifreeze you should find out the exact place of leakage because your engine can overheat and you'll pay a lot of money for repair. If you are not able to find the place if leakage you should try it if it it can leak from the nipple and it is easy to fix it, if no, you should ask [link|https://www.spartamech.co.uk/air-conditioning/|some specialists]