FINDLAY, Ohio (AP) - A pipeline subsidiary of Marathon Petroleum Corp. is rising in its stock market debut after raising $380.6 million in an initial public offering of its units.

MPLX LP sold 17.3 million units at $22 each, above the expected range of $19 to $21, which suggested strong demand for the company. The banks managing the IPO may buy another 2.6 million shares.

Public shareholders will have a 23 percent limited partner interest in MPLX, while Marathon will own the rest. Marathon Petroleum, which separated from Marathon Oil Corp. in July 2011, refines oil and transports it. It formed MPLX recently to operate pipelines.

Trading under the "MPLX" symbol, units are jumping 22 percent to $26.73 in morning trading. Marathon Petroleum shares are up 2 percent to $55.08.