I just picked up a new 09 Legacy 2.5 Special Edition with a 5-speed and I want to find out when I should do first oil change? Engine is non turbo 2.5 liter. I don't want to wait until recommended 7500 mile change...when should I get rid of the factory fill? I have a 5 quart jug of Pennzoil YB 5w-30 ready to go. Car was built on 12/08 so the oil is over 6 months old.