I would use the Mathilda Shell Gas/Filling/Petrol Station which is conveniently located near the 101-N highway, so you can get right on the freeway to the airport (SFO).
The airport is still close enough that your gas indicator will be on the "F", so no gas charge.
The Mathilda Shell station is located here:
776 N Mathilda Ave, Sunnyvale, CA 94085-3510
Directions from the Yahoo! Sunnyvale office to station:
http://maps.yahoo.com/dd_result?newaddr=701+First+Avenue&taddr=776+N+Mathilda+Ave&csz=94089&country=us&tcsz=Sunnyvale+CA&tcountry=us&oerr=-3001&name=Y%21+Sunnyvale
Onward directions to the airport:
Just turn right out of the station and the on-ramp to 101-N is on the right, just across the intersection.
Good luck!