U.S. stock index futures advanced on Friday after four consecutive days of losses, with investors awaiting Friday's key U.S. payroll report while digesting the impact of the tumble in commodity prices.

U.S. crude futures shed 2.5 percent to $97.27 and ICE Brent futures lost 2 percent to $108.56, extending a 10 percent crash on Friday, while silver earlier touched $34.23, its lowest level since March 18.

Exxon Mobil Corp dipped 0.5 percent to $82.23 in light premarket trade.

It's not completely clear that lower oil prices isn't just good for most stocks and it's possible that you could see a separation between what is happening in commodities -- at least for a while -- and some continued strength in equity prices. What you will end up with if this continues, is a shift in leadership, said Rick Meckler, president of LibertyView Capital Management in New York.

Wall Street stock indexes fell for a fourth straight day on Thursday as a massive sell-off in commodities spilled over into other markets, forcing investors out of higher-risk assets and rattling equities markets before Friday's U.S. payrolls data.

U.S. nonfarm payrolls, due at 8:30 a.m., are expected to have risen by 186,000 last month, according to a Reuters survey of economists. In March payrolls rose by 216,000 which was the biggest increase in 10 months.

The benchmark S&P 500 has fallen 2.1 percent this week on a string of soft economic data, culminating in a drop in commodity prices on Thursday as concerns over demand deterioration increased.

You'd like to see a good trend and anything that starts to interrupt that trend is going to cause some concern. When the trend starts to move the other way, you could see a much bigger correction in stocks than you are seeing here, said Meckler.

Commodity-based stocks led the S&P to a 4.5 percent gain at the start of the week after the benchmark index tested the technical support level of 1,300 on April 18.

S&P 500 futures gained 1.6 points and were above fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures added 15 points, and Nasdaq 100 futures rose 6.75 points.

Companies that have posted results on Friday include Constellation Energy Group , Northeast Utilities , Pepco Holdings

, with The Washington Post Company still expected to report.

Through Thursday, with 421 of the S&P 500 companies having reported quarterly earnings, 68 percent had profits that beat Wall Street expectations, according to Thomson Reuters data.

European shares dipped as caution prevailed ahead of the U.S. payrolls report which could point to a slowing of momentum in the world's largest economy. <.EU>

Asian equities clawed back up from the day's lows as market players squared positions before U.S. payrolls data.

( Reporting by Chuck Mikolajczak, Editing by Chizu Nomiyama)