[joelwtk]

Hi everyone. I recently bought a 2008 323i. It has 60000km on it which is 37000 miles. It seems to be consuming much more fuel than it should be. I'm doing maybe 80/20 suburban/highway driving. No inner city driving though. I don't generally drive in very much traffic. I drive cautiously and don't push the car; this is the main reason why. I'd love to push it but the consumption is just so bad, which is why this is so frustrating.

Anyway, my car is getting 15mpg which is 15L/100km. This seems overly high to me.

I haven't driven the car extensively (About 800km). Although I acknowledge this is a factor, surely it wouldn't impact the consumption to the point that it is 15L/100km. I was expecting at least 20mpg or 11L/100km.

I've run my own calculations so I know that the OBC is accurate.

So far, I've replaced the spark plugs, air filter, cleaned the MAF sensor, and inflated the tires to their correct psi.

My local BMW dealership ran a diagnostic and found no codes on the engine.

Please, if anyone can provide some insight, it would be amazing. I seriously don't know what to do next. Would the O2 sensor do much? Can anyone provide insight to just how much driving the car more would give it better economy?

Cheers.

[PhaseP]

Is your engine direct injected? One possibility for high fuel consumption could be leaking injectors. Direct injectors I hear are more likely to leak. So should check for that.

Another thing that comes to my mind is to check your if you have exhaust leak close to any 02 sensor.

I had my exhaust flanges completely rusted where the collectors after the first set of catalytic converters connect to the mid pipes just beside the transmission and this year they started to slowly come apart. The post cat 02 sensors are very close to this flange connection. The leak from the exhaust there were throwing off the 02 sensors causing engine running rich and consuming more fuel than necessary. But I had eventually had a rich code from the computer, and was finally starting to hear the exhaust leak noise from the separating flanges.

The computer throws error code if the rich (or lean) condition is more than 20% out of expected. (Not sure about the percentage but something like that.) You may be below the threshold. But if you can monitor the parameters as the engine is running you will know if it is running rich and how much. The dealership would have been able to find this out.

[joelwtk]

Originally Posted by PhaseP

Is your engine direct injected? One possibility for high fuel consumption could be leaking injectors. Direct injectors I hear are more likely to leak. So should check for that.

Another thing that comes to my mind is to check your if you have exhaust leak close to any 02 sensor.

I had my exhaust flanges completely rusted where the collectors after the first set of catalytic converters connect to the mid pipes just beside the transmission and this year they started to slowly come apart. The post cat 02 sensors are very close to this flange connection. The leak from the exhaust there were throwing off the 02 sensors causing engine running rich and consuming more fuel than necessary. But I had eventually had a rich code from the computer, and was finally starting to hear the exhaust leak noise from the separating flanges.

The computer throws error code if the rich (or lean) condition is more than 20% out of expected. (Not sure about the percentage but something like that.) You may be below the threshold. But if you can monitor the parameters as the engine is running you will know if it is running rich and how much. The dealership would have been able to find this out.

Okay, cheers for your reply.To add, the car only has 60,000km's on it (37000 miles) to add some context. And yes, NA I6 2.5L engine.

[mecheng77]

Reset the meter and check on a highway drive.
I get 30mpg on highway but sometimes less than 20mpg in the city depending on the weather. These cars are terrible in the city, great on the highway