BOSTON (TheStreet) -- David Tepper, the billionaire founder of hedge-fund firm Appaloosa Management, is considered by some to be the world's savviest investor.

The so-called deep-value style practiced by Tepper, a former trader at Goldman Sachs ( GS), helped his firm outperform rivals last year. All four of his funds doubled after he purchased financial shares during the stock-market low in March. The S&P 500 Index, in contrast, rose 26% after crashing 37% in 2008.

During the fourth quarter, Tepper bought airline stocks Delta ( DAL - Get Report), which is up 74% in six months, and UAL Corp. ( UAUA), which has surged 161%.

Tepper's picks and timing have been impeccable during the past year. He added positions in two small-cap refiners during the first quarter. The two process crude oil into gasoline, jet fuel and diesel fuel. Each operates a network of retail gas stations. Here's a closer look at Tepper's new bets.

Tesoro ( TSO) is a San Antonio-based refiner. It has a market value of $1.8 billion.

Quarter: Tesoro swung to a first-quarter loss of $155 million, or $1.11 a share, from a profit of $51 million, or 37 cents, a year earlier. Revenue grew 41%. The operating margin fell from 3.5% into negative territory. Tesoro holds $290 million of cash and $1.8 billion of debt, converting to a debt-to-equity ratio of 0.6.

Stock: Tesoro has fallen 24% during the past year, underperforming U.S. stock-market benchmarks. It trades at a price-to-book ratio of 0.6 and a price-to-sales ratio of 0.1, 79% and 95% discounts to peer averages. It's also cheap based on projected earnings and cash flow. The shares have a beta value of 1.3, tending to magnify the market.

Consensus: Of analysts covering Tesoro, two advise purchasing its shares, 17, or 81%, recommend holding and two suggest selling them. Goldman Sachs expects the stock to gain 27% to $16. Citigroup ( C) and Deutsche Bank ( DB) expect Tesoro to hit $15. Of the stock's 15 largest holders, 10 purchased more stock during the first quarter.
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Sunoco ( SUN - Get Report) is a Philadelphia-based refiner. It has a market value of $3.7 billion.

Quarter: Sunoco swung to a first-quarter loss of $63 million, or 34 cents, from a profit of $12 million, or 2 cents, a year earlier. Revenue expanded 42%. The operating margin narrowed from 2.2% to 0.4%. Sunoco has $812 million of cash and $2.5 billion of debt, translating to a debt-to-equity ratio of 0.9.

Stock: Sunoco has risen 7% during the past 12 months, lagging behind U.S. benchmarks. It sells for a price-to-sales ratio of 0.1 and a price-to-cash-flow ratio of 3.2, 94% and 61% discounts to industry averages. It's also cheap based on book value, but costly when considering projected earnings.

Consensus: Of researchers following Sunoco, three rate its stock "buy," 12 rate it "hold" and five rank it "sell." Credit Suisse ( CS) offers a price target of $39, leaving a potential 29% return. Morgan Stanley ( MS) expects the stock to hit $36. During the first quarter, eight of the 15 largest holders purchased more shares.

-- Reported by Jake Lynch in Boston.
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