From time to time we read about, and bring you news about, companies in our industry floating “notes”–what we call IOUs–a form of debt used to finance new spending or (in this case) refinance and pay off older debt. We’re not high finance experts, but it always looks to us like an elaborate shell game of robbing Peter to pay Paul. Just kick the debt can on down the road. But so many companies do it, there’s obviously some advantage. The latest, and biggest by far we’ve seen, is MPLX (MarkWest Energy). They just announced they are floating a whopping $2.25 billion of “unsecured senior notes.” MPLX will use $750 million of it to pay off older notes, and the rest to repay loans borrowed under the company’s revolving credit facility, and repay loans made to parent company Marathon Petroleum.