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BMW 3-Series and 4-Series Forum (F30 / F32) | F30POST > Technical Forums > N47 and N57 Turbodiesel Engine / Drivetrain / Exhaust Modifications > F30 320D Auto Poor Fuel Consumption
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      12-24-2017, 03:58 AM   #1
MalcForrest
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F30 320D Auto Poor Fuel Consumption

Hi guys,

I'm new to the forum and also as a BMW owner. I've recently purchased a
2015 BMW 320D Msport Auto, blue performance and in the month of owning it, the fuel consumption seems very heavy.

If I leave it in auto the gear changes seem either too late before changing up or it will drop a gear too soon where it could have held it longer and used more of the torque available.

At the moment I'm getting 43 mpg with a mix of short/long journeys. he second I start the car and drive off unless i'm super careful the fuel consumption reduces like a lead balloon.

The other thing i've noticed is that the turbo makes some amount of compression blow back (Flutter).

Am I being paranoid?
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      12-24-2017, 11:45 AM   #2
floydarogers
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Quote:
Originally Posted by MalcForrest View Post
...
I'm new to the forum and also as a BMW owner. I've recently purchased a
2015 BMW 320D Msport Auto, blue performance and in the month of owning it, the fuel consumption seems very heavy.

If I leave it in auto the gear changes seem either too late before changing up or it will drop a gear too soon where it could have held it longer and used more of the torque available.

At the moment I'm getting 43 mpg with a mix of short/long journeys. he second I start the car and drive off unless i'm super careful the fuel consumption reduces like a lead balloon.

The other thing i've noticed is that the turbo makes some amount of compression blow back (Flutter).

Am I being paranoid?
43 UK is like 35 US, so that's about what my wife's 2014 328xd (US nomenclature - same engine) gets. She has a very soft foot and runs with ASS on and her car is sitting 36.5 for it's lifetime of 30K miles with us. We get well over 40mpg when highway only (probably 45 or more at 60-70 mph).

Winding up the revs beyond 3K isn't necessary - that's actually beyond the torque peaks. Yeah, the HP peak is up there at around 4K or so but it's generally unnecessarily to go up there.

If you have the three modes, try driving in Eco Pro mode and see what it does to throttle management and shifting. You've got full torque at 1200 to 2500 or so, and you should be in there all the time for max economy.
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      12-25-2017, 01:23 PM   #3
stylinexpat
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When accelerating in any mode on my 328d I have found that 10% to 25% throttle max is all you need to get good fuel economy. Torque numbers are down low so you do not need to mash the pedal down to accelerate like you do with most abs engine cars. I can do 80-85 MPH on freeway and still get 48 MPG here in America. The car gets great fuel economy. On the freeway when you are at cruising highway speeds you do not need any other mode besides Eco Pro. Whether you are in Eco Pro mode or Sports mode you are still doing the same speed.

In the city from traffic light to traffic light you need to get used to making good use of gas pedal. Push down about 10% and hold there you will see that car will accelerate fairly quickly up to 70-80 MPH if kept down at 10%. I reckon 25% max. At 25% throttle the car will accelerate to over 100 MPH. There really is no need to push the pedal any further unless you are racing someone or have an urgent need to accelerate. Even then the difference is not huge.

If I get some time I will try to demonstrate one and upload a video.
As you can see in image attached at 80 MPH I can still get 49 MPG which in my opinion is amazing.
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      12-26-2017, 09:23 AM   #4
jnecr
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Quote:
Originally Posted by MalcForrest View Post
At the moment I'm getting 43 mpg with a mix of short/long journeys. he second I start the car and drive off unless i'm super careful the fuel consumption reduces like a lead balloon.
Sounds pretty normal for mixed city/motorway driving. What's the temp been like? Cooler weather definitely makes it harder to get good fuel mileage.

I've had ~50mpg on pure interstate driving and ~35mpg with mostly city driving. Both seem pretty normal to me coming from two VW TDIs previously.
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      12-27-2017, 01:22 AM   #5
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Dropping down to about 70 MPH I was able to get high 50's on a straight away and mid 60's on a downhill. Fuel economy is solid on this car and handling is very good. Same chassis they used for M3 and made in Germany where all other 3 Series come out of Africa now besides this one and the M3/M4
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