Crazy mileage when idling. Mileage meter malfunctioning?
01-13-2011, 12:42 AM
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When I'm idling (800-900rpm), the analog meter displays no gas usage. But the digital meter in the dash always climbs up to the insanely low mileage. In my case 50L/100km, which is 4,7 MPG (US gallon). This is either insane or incorrect. Why would an idling engine need so much fuel?
How to test:
1) reset your mileage meter
2) stay idle
3) watch the digital meter as the number climbs
Because of this issue, average mileage is totally off. I stop at 3 stoplights during a normal trip and obviously the whole average is completely misleading from that point.
How to test:
1) reset your mileage meter
2) stay idle
3) watch the digital meter as the number climbs
Because of this issue, average mileage is totally off. I stop at 3 stoplights during a normal trip and obviously the whole average is completely misleading from that point.
01-13-2011, 06:16 AM
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My Ride: 545iSMGSilver GrayAuburn Dakota LeatherLogic 7 Premium SoundSports Package
It's correct. Think about it. You are not moving. Essentially driving 0 miles but burning gas to keep the engine running. You really should be getting 0mpg but because the car does an average over a period it'll show some number in your case 4 mpg
01-13-2011, 06:43 AM
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Simple explanation. I understand. However this causes the averages to be completely "inaccurate" (misleading is a better word) especially for European l/100km unit. It would be smarter from the BC meter to not count in any averages or switch to a hourly unit counting during idling. Maybe it's not the BMW to blame, but the algebra. Averages are "misleading". 
01-24-2011, 03:43 PM
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My Ride: 2012 535i X-driveSpace Grey/Black Dakota, Fineline Anthracite Trim; Executive Package (Rear View, Lumbar, Nav, Voice, SIRIUS, HiFi Pro) Technology Package (Hi Beam Assist, Lane Departure, Blind Spot Detection, Surround View) BMW Apps (Apps, Smart Pho
Model Year: 2012
My car only goes to either 39.9L/100km or 40L/100km. The problem is with reality and not the car. As stated, if you are not moving your mileage should be infinitely higher than even 40L/100. The only way to "more accurately" measure mileage is with a lot of miles when the car is moving; for example, after each fill-up and the mileage is a mix of idling and moving. The meter isn't bang on perfect but it does give a good representation of your mileage. After your next fill-up, reset the odometer and then when empty again use that fill-up to manually determine your mileage without the benefit of the computer. The figures aren't too far off but they will never be 100% accurate. You can't eliminate the stop portions because the fuel is still being burned. Thats why a hybrid gets good mileage since the engine is actually off for those times the car is stopped. I'm not convinced the 'moving' mileage in a hybrid is any better than other cars.
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