https://www.fool.com/investing/2018/10/19/this-refining-giant-is-the-latest-energy-company-t.aspx :

Valero Energy launched Valero Energy Partners in late 2013, joining its refining rivals in creating an income-producing vehicle that would steadily buy its parent’s midstream assets. Since that time, Valero has regularly sold its logistics assets to its MLP, which gave it the cash to buy back more stock and fund expansion projects. Meanwhile, Valero Energy Partners used those acquisitions to fuel fast-paced distribution growth, boosting its payout by 159% since its formation.

— Other MLPs:

• MPC -> MPLX
• PSX -> PSXP

Phillips 66 and Marathon Petroleum have both shifted their strategy by using their MLPs as funding vehicles for organic growth projects. That has enabled both companies to further diversify into the midstream sector without investing that capital on their balance sheet. It’s a move that should help those refiners produce steadier earnings going forward.