In city the 8th gen does 12.5 to 13 happily (without air con) and the 1.6 altis is doing 10-11ish inside city.
Grande has cvt so its supposed to do better. The car in talk here is 1.6 altis i believe.
P.s you need to get your 8th gen civic checked. Mine did 400km in half talk from lhr to isb. A and does 270-310 in half tank inside islamabad local driving. 8th gen civic is my daily runner