Go SC and ask them to reset the previous owner campro setting.

1) How old are the tires? But then again, second hand, not surprising I guess.

2) Your rev going up and down on the 2K to 3K RPM is probably due to your car switching between 1st and 2nd gear.

3) That mileage you posted, when you started, was it a confirmed full tank? Did you fill it in yourself? If not, you can try following the formula:-
a) Fill full tank
b) Reset odometer
c) Drive normally until your normal refueling point.
d) Refill full tank
e) Make a note of how much you refill and how much your mileage at refill. This will be the basis of your calculation of fuel consumption
f) Repeat steps (b)  to (e) at least 3 times to get an average.

Always stick to the above formula for FC calculations.
Always use km/l to make your fuel calculations, NOT cents/km because fuel prices fluctuate, rendering previous calculations obsolete.

4) If the FC is a concern to you, make a point to:-
a) Control your right foot. Try to keep revs under 3K.
b) Always keep your tire pressure optimum. You can find the tire pressure guide sticker in the driver side, rear passenger door frame.
c) Plan your trips and avoid traffic jams whenever possible.

Congratulations on your new car. Overall, I'm happy with my car and I hope that you'll be happy with yours. Good luck and hope you stay happy with it.

Just get new car sure vr hard to resist the temptation of harassing your oil  pedal

what kind of problem? gear shifting feels?