MPG drop

k31ron · 07-18-2016, 05:01 PM

Wonder if anyone has any ideas.. my 2011 330d has now reached 80k miles and over the last month the mpg has rapidly dropped. I do the same 1 hour 90 % motorway commute sat on cruise control at the same speed in similar traffic. For this journey I used to average 44+mpg but now its dropped to a consistent 39mpg over last month (and its not air con). Wondered if there are any obvious things to check? Seems to be running fine.

mjn77 · 07-18-2016, 05:07 PM

Sticky caliper?
Not getting up to temp?

Rustymage · 07-19-2016, 03:15 AM

Poor quality fuel
Injector issue
Fuel filter clogged
Air filter clogged
Roof box fitted
Carrying something in the boot (body?)

Or

You've gotten very fat!

BMW Steve · 07-19-2016, 04:07 AM

TIME TO DO A LITTLE PREVENTATIVE MAINTANANCE,

When my 530d had some similar symptoms I decided to replace the EGR Thermostat, the fuel filter, I then had it terror cleaned, the MPG went back up and the car performed a little bit better.

Soon after though I also replaced the water pump, main thermostat and the utility belts as a little preventative maintenance as it was near 90K,

A little OCD I know....

AWSAWS · 07-19-2016, 05:41 AM

Maybe try some injector cleaner as well. Worth a shot. I wouldn't bother with the redex stuff. Do some research and see what's best. For petrols it's something with lots of PEA in it. Like Redline S1.

djgandy · 07-19-2016, 05:57 AM

This thread may be of interest to you - http://www.e90post.com/forums/showthread.php?t=1266776

Gear Head · 07-19-2016, 12:58 PM

Been using your air-con more recently? Try turning it off when cruising. Usually makes around 3-4mpg difference.

k31ron · 07-20-2016, 04:04 PM

Thanks guys, not sure my recent pie binges would justify all of the drop... But probably cover 1 mpg. Might give that ar6400d ago, always a skeptical of that kind of thing but it will be a good test.

07-18-2016, 05:01 PM	#1
k31ron Enlisted Member 4 Rep 44 Posts Drives: 330d MSport Join Date: Oct 2014 Location: derbyshire iTrader: (0)	MPG drop Wonder if anyone has any ideas.. my 2011 330d has now reached 80k miles and over the last month the mpg has rapidly dropped. I do the same 1 hour 90 % motorway commute sat on cruise control at the same speed in similar traffic. For this journey I used to average 44+mpg but now its dropped to a consistent 39mpg over last month (and its not air con). Wondered if there are any obvious things to check? Seems to be running fine.
	Appreciate 0 Tweet Quote

07-18-2016, 05:07 PM	#2
mjn77 Colonel 1454 Rep 2,044 Posts Drives: E90 M3 LCI Jerez Black Join Date: Apr 2015 Location: Herts, UK iTrader: (2) Garage List 2011 BMW M3 [10.00]	Sticky caliper? Not getting up to temp?
	Appreciate 0 Quote

07-19-2016, 03:15 AM	#3
Rustymage First Lieutenant 30 Rep 294 Posts Drives: BMW 330i E90 Join Date: Jul 2016 Location: Cambs iTrader: (0) Garage List 2006 BMW 330i [0.00]	Poor quality fuel Injector issue Fuel filter clogged Air filter clogged Roof box fitted Carrying something in the boot (body?) Or You've gotten very fat!
	Appreciate 0 Quote

07-19-2016, 04:07 AM	#4
BMW Steve Captain 120 Rep 968 Posts Drives: F11 535D & e93 335i Highline Join Date: Sep 2011 Location: Witlshire UK iTrader: (0)	TIME TO DO A LITTLE PREVENTATIVE MAINTANANCE, When my 530d had some similar symptoms I decided to replace the EGR Thermostat, the fuel filter, I then had it terror cleaned, the MPG went back up and the car performed a little bit better. Soon after though I also replaced the water pump, main thermostat and the utility belts as a little preventative maintenance as it was near 90K, A little OCD I know....
	Appreciate 0 Quote

07-19-2016, 05:41 AM	#5
AWSAWS Colonel 277 Rep 2,340 Posts Drives: E92 GC Turbos, FBO, 335i DCT Join Date: Nov 2012 Location: Valhalla iTrader: (0)	Maybe try some injector cleaner as well. Worth a shot. I wouldn't bother with the redex stuff. Do some research and see what's best. For petrols it's something with lots of PEA in it. Like Redline S1. __________________ GC Turbos, FBO, JB4, DCT, Port Meth injection, BMS Charge Pipe, NGK plugs. EBC brakes and pads, LED Angel lights, LED foglights, LCI rears OCC, Braided brake lines. Custom Diff Lockdown Kit, VTT inlets, TMAP, stage 2+ fuel pump 11.79@119mph (stock turbos) 11.74@129mph (GC Turbos)
	Appreciate 0 Quote

07-19-2016, 05:57 AM	#6
djgandy Colonel 142 Rep 2,335 Posts Drives: E93 M3 Join Date: Aug 2012 Location: London iTrader: (0) Garage List 2011 M3 [0.00]	This thread may be of interest to you - http://www.e90post.com/forums/showthread.php?t=1266776
	Appreciate 0 Quote

07-19-2016, 12:58 PM	#7
Gear Head Private 6 Rep 59 Posts Drives: E92 325i M Sport Join Date: Sep 2015 Location: Kent iTrader: (0)	Been using your air-con more recently? Try turning it off when cruising. Usually makes around 3-4mpg difference.
	Appreciate 0 Quote

07-20-2016, 04:04 PM	#8
k31ron Enlisted Member 4 Rep 44 Posts Drives: 330d MSport Join Date: Oct 2014 Location: derbyshire iTrader: (0)	Thanks guys, not sure my recent pie binges would justify all of the drop... But probably cover 1 mpg. Might give that ar6400d ago, always a skeptical of that kind of thing but it will be a good test.
	Appreciate 0 Quote