An internal oil filter is installed at least partially inside a crankcase and/or an oil sump of a compressor. The internal oil filter can receive oil from an oil pressure regulator and filter the oil via filter media. The received oil radially penetrates through the filter media and flow directly into the oil sump from an outside surface of the filter media. This can eliminate the need of fluid lines connecting an outlet of an oil filter to the oil sump and any sealing mechanism therebetween.