SOUNDS LIKE THE GASKET FROM THE OLD OIL FILTER DECIDED NOT TO RELEASE SO NOW YOU HAVE TWO OIL FILTER GASKETS AND THAT'S WHERE THE LEAK IS COMING FROM MAYBE PERHAPS??
HIGHWAY MILEAGE IS GOING TO DEPEND ON YOUR CRUISING SPEED ALSO OF COURSE. IF YOU KEEP THE CRUISE CONTROL SET AT 65MPH, YOU SHOULD AVERAGE 26MPG USING 87-91 OCTANE DURING SPRING FALL SUMMER MONTHS
THE ONLY WEIRD LITTLE POINT HE MAKES IS HOW TO CLEAN OUT A PAPER FILTER BETWEEN ACTUAL CHANGES, HE SUGGESTS A VACUUM CLEANER?? HAHAHAAH HOW ABOUT COMPRESSED AIR YOYOYO