On Petrol i do not think that its necessary to warm the engine (except very cold weather).

Better to Sale your City and Buy Aqua or FIT

mostly it depends on the driving pattern
light foot will help u the max
btw my friend owned 10 model
he used to really hypermile
like 22-kml
also he is getting 23kml on PKDM wagon R

Don't warm up your car before driving - that is one of the biggest reasons for your high fuel consumption. Just start, put it in gear, and drive off gently. Keep the rpm low on a cold engine - generally not more than 3k at max (preferably less than 2k).

When anticipating a stop, or a checkpost, stop accelerating. Bleed your speed gradually in gear before braking.

Drive at just enough speed to keep up with traffic - your average speed will hardly vary in city driving in most situations.

Oh, and 22 kml is a piece of cake for a Honda City. You don't need to drive on the highway to achieve that - with the right knowledge and enough practice you can actually exceed that in city driving.

Read twice to check that you are indeed saying 12Km / L. Is'nt that low for a City ? I have 1.8 Civic manual and have 205 tires and I definitely do not have a light foot. It gives me around from 10.5 to 11 Km / L within city and 13.5 on motorway.

I guess then it seems ok.

for your question number 3 the answer is 30 seconds! iv read many other professional forums too where this question has been asked and the answer is 30 seconds when u start the car in the morning! anything more than 30 seconds is wasting fuel! u dont need to idle for 2-3 minutes! woh poranay zamanay ki gadiyoon mein hoa karta tha carburetor wali mein and when efi technology wasnt that advance!

Basically a driving a cold engine makes no difference then manufacturers shud remove the cold engine light

So the tip from my side

Drive with a warmed up engine & try to drive with RPM under 1.5K preferrably 1.25K

results will be beyond par

QUALITY JDMs @ fb.com/mycar.pk

at cold start rpm goes higher than normal n comes back to normal after the engine reaches it optimal operating temperature..
give ur car a litlle time at cold start to warm up a bit... let say let the temp needle starts to move !
good for ur ride's engine health ! agr aese e chalana sahi ho to rpm ko optimal temp pe lanay ki kia zrurat,bnao f16 phr

I usually dont have the patience to drive slowly , but a buddy of mine who is a hyper milling freak , told me once .. to get the best average
change gears at 2k rpm .. and drive as if you have no brakes..

Now to elaborate on the no brakes part , its like if you see a check post of a red traffic light ahead simply lift off the accelerator and let the car slow down on its own a bit and gently apply the brakes..

So basically no sudden accelerations , no sudden brakes ..
Just my 2 cents