High Fuel Usage

[ben_t]

I have a problem with high fuel usage.
I seem to be using twice as much fuel as I should be. Even though according to the OBC I am running quite efficient eg highway driving at 90km/h I am using approx 8l/100km.
I suspect it may be a fuel leak but when I get under the car for a look I can't smell any petrol.
Would a faulty oxygen sensor cause high fuel consumption (running rich?) but I don't appear to have high fuel comsumption according to the OBC?
Where is the sensor for the fuel comsumption? If I don't have high consumption then I could have a leak between the fuel tank and the sensor.

Any other ideas?

[CosmosBlack]

Yes, bad O2 sensors could cause poor gas consumption. What mileage are you at now? If you're close to around 100k, the O2 sensors are about done. But the service engine soon light will come on. Bad O2 sensor symptoms include rough idling.

[bad man working]

There's no sensor for the consumption it's either calculated from the amount of fuel in the tank and the mileage or on later cars it's taken direct from the amount of time the fuel injectors opened for.
Only one way to test consumption accurately run the car out of fuel pour in a measured gallon and drive till it runs out again and check the mileage don't forget to take another can full for when you run out the 2nd time.

[billB]

Is it possible to do it the other way around? By filling the tank up (yourself) then drive it for say 100 Miles then fill it up again at the same station/same tilting position of the car facing the pumps. then devide miles by gallons consumed! I ran out of Gas once in Frankfurt/Germany (faulty gas gauge) cost me $50DM (police ticket) back then in 1970s-no Euros then.

[ben_t]

After manually checking my fuel consumption, it gave me 17l/100km. This is about 50% more then what the OBC tells me.

I drive a mixture of city and highway driving, however work is only 20 minutes from home so maybe the engine has not warmed up and hence is still running rich???

The problem is that the idling is fine, acceleration is fine but the fuel consumption is too high. Could this still be a faulty O2 sensor? (I thought the signs of a faulty O2 sensor is poor acceleration, rough idling and high fuel consumption?)