As investors, we need to understand how our companies truly make their money. A neat trick developed for just that purpose -- the DuPont formula -- can help us do so.

The DuPont formula can give you a better grasp on exactly where your company is producing its profit, and where it might have a competitive advantage. Named after the company where it was pioneered, the formula breaks down return on equity into three components:

Return on equity = net margin x asset turnover x leverage ratio

What makes each of these components important?

  • High net margins show that a company can get customers to pay more for its products. Luxury-goods companies provide a great example here.
  • High asset turnover indicates that a company needs to invest less of its capital, since it uses its assets more efficiently to generate sales. Service industries, for instance, often lack big capital investments.
  • Finally, the leverage ratio shows how much the company is relying on liabilities to create its profits.

Generally, the higher these numbers, the better. That said, too much debt can sink a company, so beware of companies with very high leverage ratios.

Let's see what the DuPont formula can tell us about Western Refining (NYSE: WNR) and a few of its sector and industry peers:

Company

Return on Equity

Net Margin

Asset Turnover

Leverage Ratio

Western Refining 3.8% 0.3% 2.85 4.10
Frontier Oil (NYSE: FTO) 21.8% 3.3% 2.88 2.27
Tesoro (NYSE: TSO) 7.4% 1.1% 2.51 2.81
Valero Energy (NYSE: VLO) 7.4% 0.6% 2.34 2.54

Source: Capital IQ, a division of Standard & Poor's.

Low net margins, high asset turnovers, and high leverage -- that looks like the story of these energy players. Western Refining has the lowest ROE of this group, mainly because of its low net margin, since its asset turnover and leverage sit at the upper end of those of its peers. With much less leverage and a higher margin, Frontier leads this group with a solid ROE. Tesoro and Valero look much the same in these metrics.

Using the DuPont formula can often give you some insight into how a company is competing against peers and what type of strategy it's using to juice return on equity. To find more successful investments, dig deeper than the earnings headlines. If you'd like to add these companies to your watchlist, or set up a new one, just click here .

Jim Royal, Ph.D., does not own shares in any company mentioned. The Motley Fool owns shares of Western Refining. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.