The problem I had with the later races during the series is after the third race, your oil is shot.
At that point you're at a 50hp disadvantage.
Suzuka is the one track where you really don't have corners to cut (or stupid AI that don't know how to take a chicane).
I ended up doing it by itself rather than with the championship. Literally had to do 20 clean laps. 2nd place was behind about 3-5 seconds the entire time.