MPG down (petrol)

answers in line

Andrew Rolland wrote: That's not great mpg, I am getting about that on mine at the moment but I'm doing much shorter runs these days.   Could be tyre pressures, different tyres, wheel bearing on its way out, binding brakes, small air or vacuum leak. car is tip top shape AFAIK, other than mpg dropping  Could be a spark plug or coil on its way out, it could be loads of things. thats what i was thinking, but cant think of a way to test other than replace? You haven't added any chaved accessories which has increase weight and drag, like body kits or spoilers or a loud exhaust or a modified air filter? certainly not!   Was it good quality oil you used in your service? BMW spec AFAIK - thats the risk of not doing it yourself....   Is the traffic worse? Are you mibbie doing more stop start driving? This kills my mpg.   Is it an autobox?  Have you had the transmission serviced?  Any clunks from the drive train?  A worn CV joint on a drive shaft or UJ on the prop shaft may increase rotational resistance and burn more fuel. Manual 6 speed. no clunks or untoward noises   My mpg was much better when I first got my E60, I put it down to the fact that I mibbie drove it more gently at first until I got used to the power!

recardo wrote: My mpg has dropped quite a bit in the last 8 weeks.

Errr... if you drive a E60 525i (3.0i) M-Sport then why are you worried about MPG

When I drove my E30 M3 that was the last thing on my mind!

Just enjoy ..........

recardo wrote: err... if something deviates from "normal" wouldn't you want to know why? I do especialy when its my prized posession

My M3 was my 'prized possession', and was regularly serviced but sometimes the MPG dropped.

Reading your posts it looks similar, so my conclusion is it may be a Heavy Right Foot

Andrew Rolland wrote: Has the wife or someone else been allowed to drive it?

don't be silly - SWMBO had no idea how to change gear with their Right hand.

My car, MY car, me, ME ....... got the idea?

Andrew Rolland wrote: Get out of the way Pitsy, I wasnae talking to you

mine was the previous post, so I naturally assumed....

p.s. - next time go "@??" so we know

Edited by thepits - 31-May-2013 at 18:14

Andrew Rolland wrote: Have you changed type of unleaded, i.e. from super to normal or from a decent brand like Shell to supermarket stuff?

I know what "they" say about the supermarket stuff but IMHO I've never noticed a difference even with the E30 M3

All the modern cars have an abundance of fuel mixture influencing systems with an armada of sensors involved. You have FOUR oxygen sensors in your exhaust system for a start. If one or two of them have aged and give slightly false readings to your ECU, it may cause your mpg to change.

NOT SAYING that your oxygen sensors need changing! Just one thing which comes to my mind.

Or the airflow meter. Or the engine temperature sensor. Small item which can have a big effect on fuel consumption if engine temp is read to low and ECU thinks engine is cold and richens up the mixture.

How is your coolant temperature? I know you haven't got a gauge for this in the dash (...thanks BMW!!!) but there is a code where you can tap into the dash cluster which gives you all the readings the ECU sees.

Or you get fed up with this like I have and buy "Tourqe" app for your phone and a OBD2 Bluetooth dongle. That's how I found out that my coolant is hardly over 70 deg!

well, looks like the problem has manifested itself further / taken a turn for the worse - car was running lumpy today (on 5 cyls).
After a lot of fannying about and troubleshooting - it looks like coil no 1 is kaput.  so will get a new one tomorrow  and get back to normal!

quick question - will it be ok to drive on 5 cylinders?  nearest ECP is 15miles away




Edited by recardo - 07-June-2013 at 21:59

I'll leave the car until its sorted, managed to get a lift for the kids football duties this morning, ECP is open to 4pm so will head over this afternoon and use the wifes car or my motor bike ;)

edit_ meant to ask - there are 5 black coils & 1 grey - I take it the grey one is a newer updated design?  Its a black one that has failed.

Numbers on the coils are;
Black 7571644-01     0221 504 471     07-06-29 D  02540
Grey 7594935-02      0221 504 471    11-02-17  G 01826



Edited by recardo - 08-June-2013 at 09:01