BUZZ-HollyFrontier Corp: Wells Fargo upgrades
** Oil refiner's shares up about 1 pct at $43.65 premarket
** Wells Fargo upgrades to "outperform" from "market perform"
** Analysts say wider crude differentials and moderating natural gas prices should support better crack spreads - the difference between the prices of crude oil and the petroleum products extracted from it - in fourth quarter 2014 and 2015
** Of the 16 analysts covering the stock, four have a "buy" or higher rating, 10 have a "hold" and two recommend selling the stock, according to Thomson Reuters data
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