Rep Power: 0

Hi! 6 months ago I bought 2009 honda civic dx and I was very happy with it until December when I realized that fuel consumption is really high, I was making 400km on a full gas tank (40l) about a week ago fuel consumption get even worst! Right know I'm making 300km on a gas tank! Crazy! Air filter is clean, spark plugs and fuel injectors replaced. Not sure if this is connected but I also have a problem with a heating system. When I'm parked even when my engine is warmed up, (gauge half the way on the scale) when I crunk up heat the gauge can slowly drop to zero. Did any one here have had the same problem or know what can be wrong with my car?

 
Rep Power: 223

Yeah that's some pretty terrible fuel economy. A few things to check:
-Check engine light on? Fault codes?
-Any brakes dragging or other issues? Jack the car up and put it in neutral, all four wheels should spin fairly freely.
-Tires properly filled?
-Are you letting it warm up for a long time before driving? This will hurt fuel economy.

As for the heat issue:
-Coolant levels full?
-Thermostat stuck open?
-How cold is it there? These engines aren't big and can struggle to keep warm in real cold temps, especially if the thermostat is stuck open.

 
Rep Power: 0

No check engine light or faulty codes
Tires are filled properly
I will lift my car this weekend and check if wheels spins.
I'm warming it up usually for 5min not more so it shouldn't affect fuel economy that much.

Coolant level is ok
I replaced thermostat twice already so I highly doubt it's not working properly
it's pretty damn cold, sometimes temperature can drop to -20 -30 Celsius however I don't think this could be the reason for such a terrible fuel economy, my friend has same honda civic and she's making over 500km on a gas tank.

Thanks