oil futures edged lower friday but remained on track for weekly gains as traders weighed optimism over chinese demand against rising us crude inventories   west texas intermediate crude for april delivery cl1 cl00 clj23 fell 42 cents or 05 to 7774 a barrel on the new york mercantile exchange on track for a 19 weekly gain   may brent crude brn00 brnk23 the global benchmark was off 52 cents or 06 at 8423 a barrel on ice futures europe headed for a 17 weekly advance   back on nymex april gasoline rbj23 fell 08 to 2679 a gallon while april heating oil hoj23 declined 04 to 2855 a gallon   april natural gas ngj23 rose 2 to 2819 per million british thermal units on track for a 106 weekly advance crude logged a third straight winning session thursday “on overall market optimism over a chinese economic recovery” wrote analysts at ing in a note upbeat surveybased data on economic activity in china released earlier this week helped set the tone meanwhile the price for spot and nearby brent crude traded at a premium over later futures a condition known as backwardation that reflects increased nearterm demand they noted the spread for the nearby contract over the next month brnm23 hit a threemonth high of 66 cents a barrel on thursday at the same time positive economic data out of the us continues to stoke worries the federal reserve will be more aggressive than previously expected in its bid to bring down inflation raising the threat of a deep economic downturn