The program will add on to Findlay, Ohio-based Marathon's previous share repurchase authorization, which had approximately $2.14 billion remaining as of March 31.
"As we execute our strategic initiatives, including dropdowns of midstream assets to our sponsored master limited partnership, we expect cash proceeds from the dropdowns and limited partner distributions to fund substantial ongoing return of capital to shareholders," MPC chairman and CEO Gary R. Heminger said in a Thursday statement.
MPC said it might utilize various methods to effect the share buybacks, including open market repurchases, negotiated block transactions, accelerated share repurchases or open market solicitations for shares.
The new $3 billion share repurchase program has no expiration date, as well as the portion remaining from the previous plan, have no expiration and may be discontinued at any time, MPC said.
Marathon Petroleum's move comes as the company works through a strategic review brought about by pressure from activist investor Elliott Management.
Public companies often launch large stock buyback programs when facing activist campaigns, as the move helps to keep institutional investors from adding their voices to the insurgent's cause.
TheStreet's sister publication, The Deal, reported in January that Elliott brought its campaign public in November only after quietly pressuring MPC to launch a review for about two months.
The insurgent investor made public its desires to have Marathon Petroleum expedite the shift in assets to its master limited partnership MPLX (MPLX - Get Report) and consider a full strategic review over whether a tax-free separation of the company into three businesses would best serve shareholders over the long-term.
Since then, Marathon Petroleum has launched a strategic review of its retail gas station unit, Speedway, and vowed to accelerate its dropdown sale schedule to its MLP.
The company already announced an agreement to drop some pipeline and storage assets into MLPX for about $2 billion in proceeds in early March.
And Marathon Petroleum said it hoped to conclude the review of Speedway by mid-2017, meaning a solution could be reached sometime this summer.
It was unclear Thursday how far along Marathon Petroleum is in the review of Speedway or when the oil and gas refiner and transporter intends to announce the next phase of its dropdown program.
Marathon Petroleum did not respond to a request for comment Thursday.