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Discussion Starter #1 (Edited)
Morning all. Sorry for asking a question on my very first post. I did post on another username when I was looking to buy my car a year back, but can't for the life of my remember what it is.

Anyway, hello......

I have a 530d M sport on a 56 plate that I have been running around in for the last year. I love it. My wife has a 20d X1 that she picked up new two weeks ago and I also have an E30 track car, the Jaffa Cake, so I guess you could say we like our BMWs.

Some of you may also know me as the person who runs a large (ish) track day forum. Anyway enough of that.

My question.

In the year I have owned the car it has put in decent MPG. A large part of my use is running around town to work and collecting the kids, with the odd longer run thrown in at the weekend. On those runs the car has shown 40pmg and on one occasion 47mpg on a very long steady journey. But something has changed.

The Idrive computer reset itself from an mpg perspective a couple of months back, or I did it myself. This may be coincidental info, but I thought I would share it all the same.

Then I noticed that on longer runs I only getting just over 30mpg. Hmmmmmm.

I checked the water temp and found it to be low, so I had the thermostats changed. Now it's running at the right temp. However the mpg hasn't increased.

So I started doing my own checks on fuel put into the car, against the mileage covered and am finding the Idrive system to be a long way out. For example the system may be showing 28mpg for a tank and when working it out, it has actually done 37mpg. That's quite a difference in my mind.

So what's going on? Was the Idrive over reading in the past?

Why is the Idrive under reading now?

Is there a reset I can carry out?

Anything else?

The car is on 77k, has been well maintained and is having a service this weekend to ensure its not a clogged filter or some such thing.

Thoughts?
 

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1999 BMW Z3 Roadster 2.5
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You might be looking at an average MPG, try to reset the MPG again see if it fixes that. If your car has been running low MPG for a long time say 3K and you've only had it repaired for less then 1 K its barely going to increase.
 

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Discussion Starter #3 (Edited)
I reset using the journey computer on each fill up. The main computer I leave to tick along all the time (although I did reset it after the temp issue was sorted). It's the journey computer I'm comparing tank to tank on.
 

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Where are you located?
MPG (US) is different than MPG (UK), 28 US MPG = 33.63 UK MPG.
Maybe iDrive setting for units was reset?
Just guessing. Good luck.
 

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1999 BMW Z3 Roadster 2.5
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I'd love to see pics of the e30 btw..
 

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1999 BMW Z3 Roadster 2.5
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ouuuuu you scratched my itch well...
 

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hats off on the car. Love the E30. love what you've done, tasteful track car appearance looks like its tasteful under the hood too!
 

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Discussion Starter #11
Well you guys have solved the problem for me. Good work.

Checked the units and the system had reverted to US gallons, rather than UK. I changed it back and the mpg shot up. Job done.

Thank you.
 
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