Daihatsu mira es 2014 varying fuel consumption

[TORRETO1]

Salam All,
I have mira es 2014 model. I filled its tank and reset the fuel consumption figures. For the first 150 km it showed that it was giving me 19.5 km/l but now after 250km ,the average has dropped to 16 km/l. What can be the problem and how can i rectify it?

Note: The eco idle is not working due to low amp battery and the rim size is 15.
Any help would be highly appreciated.

[sleeper]

Driving patterns can cause this variation....first 150km were driven on long less traffic roads? And the next 100 in traffic?

I would suggest to manually calc the total distance travelled in a tank and then see what avg u get

[TORRETO1]

I m thinking of doing manual calculations ,but as rim size is changed, i dont know much effect it has on odometer which would not give me accurate readings.
Any idea on how can i calculate my trips?

[hash4u]

did u upgrade from 14 rim to 15
first install some speed check app in a smart phone
and see diff in car speedo vs the app
if its way off, the mileage/avg you see wld be in accurate as well

[sleeper]

Hash....i think rims wud be changed frm 13 to 15..... 13 are stocks, right?

Toretto...chk the speed diff as advised by hash above

[TORRETO1]

Yes the rims were upgraded. I have installed an app. I will check today. Thank you sir

[TORRETO1]

I think 14 are stock. I will check the speed today. Thank you for your input.

[TORRETO1]

So i checked the speed and distance through a gps app. Drove 6 kms and the speed and distance being shown on odometer of car was accurate.
The reason i feel is that good mileage i got was on canal rd and dha roads ,meanwhile when i went to rushy areas two to three days in a row the average dropped.
Can there be any other reason? And do i need to change the rims and tyres?
Another thing, when i turn on the heater, i feel like vents are choked as there is more sound than air coming out of the wents, should i go for a air filter change( the one under the dash)?