My M30 uses 20.5L/100km (11.5 miles a gallon)

[F4Phantom]

Is this normal. I think it may be a bit thristy. If it turns out thirsty what are the basics to check. Eg, injectors, air filter, fuel filter?? In my diesel 4x4 the air filter has massive impact on economy so I checked mine and it's good. The engine has done 270,000km/ around 170,000 miles so it aint new any more. I suspect a high km engine just tends to use a bit more. Thanks.

[ericcamaro]

thats excessive, Start with air filter, then fuel filter, then do your Oxygen sensor, then check the ignition system (cap, rotor, plugs, wires..etc). if none of that pans out check out your injectors make sure you dont have one stuck open, but it should be apparent when you pull the plugs if a cylinder is running rich. If an injector is stuck open the spark plug usually looks really clean, as if it was sprayed with a solution over and over to flush out all the carbon. let us know what it turns out to be, i got my money on the o2 sensor.

[Gayle]

I want to hear the answers to this because I consider my gas mileage pathetic--18mpg with majority highway miles but I am a spirited driver.

(Lately I have really been enjoying leaving tail gating trucks in the dust on freeway exchanges where my car really holds the road on the curve and they don't. Then polish it off with a pedel to the metal monent when I hit the new freeway.)

Mine has under 100k miles and is a chipped 535. Those premium gas prices are painful. Have been thinking it is time to pull out the prior owners maintence records and see if the oxygen sensor has been changed.

[angrypancake]

18 pathetic? i'm lucky to get 14....

[Gayle]

18 pathetic? i'm lucky to get 14....

on the razor scooter???

[F4Phantom]

thats excessive, Start with air filter, then fuel filter, then do your Oxygen sensor, then check the ignition system (cap, rotor, plugs, wires..etc). if none of that pans out check out your injectors make sure you dont have one stuck open, but it should be apparent when you pull the plugs if a cylinder is running rich. If an injector is stuck open the spark plug usually looks really clean, as if it was sprayed with a solution over and over to flush out all the carbon. let us know what it turns out to be, i got my money on the o2 sensor.

I think I will check my O2 sensor - thats the thing plugged into the exhaust right? I will also change my fuel filter and see where that leads me. One potential problem is that these figures are off the OBC. Could this be wrong? I have done some mental arithmetic and it does not seem to be out by much but I do remember a post where someone was talking about changing a figure used by the OBC to run in it's calculations.

[Alexlind123]

The OBC shouldnt be off by more than a few percent...

[BillionPa]

any of you single fuel filter people thought about modding to a dual parallel filter system like the V8s use?

oh and yeah, i'd check the O2 sensors, because it wouldnt be the air filter, but it could be the air sensor giving a faulty base reading, and the O2 sensor too messed up to compensate.

after you replace the O2 sensor(s), do an ecu reset.

and if you want to experiment, adding 3oz of acetone per 10 gallons of gas changes the surface tension of the gas without altering the octane rating, allowing the gas to vaporize better, and therefore less of it needed to produce the same amount of power.

and yes i have actually tested it myself, my gas mileage went up 16%

[Paul in NZ]

i am averaging about 20 mpg but that to an imperial gallon,most of it petty easy driving too,not much stop start

[pundit]

My 535i auto gets around 14.5litres/100km (about 20 mpg) driving between Emerald in the Dandenongs and Burwood commuting to work in 50/50 semi cruise/peak hour traffic.
I can get bewteen 9.5 and 10.5 litres (30-27mpg) at 100kmh and 115kmh respectivley when highway cruising.