Engine: D5: Strange mpg and other issues...

[Bashy]

Hi folks,

Firstly, I am an avid watcher of the "instantaneous" mpg, for about the last 6 months it's started fluctuating by a decent amount.

Example, on a frequently run level road in cruise control mode at 60mph it would normally be around 40 to 50mpg but it can drop to around 30 to 40mpg, but then it will climb back to the 40 to 50 mark, then drop again, what causes it to change is I think after a gear change, or if I floor it to over take, this can sometimes sort it out, or if its running right, a change in gear can make it worse.

Its not limited to 60mph, that's just an example, in a 40 limit I can put it in 6th and coast along producing 60+ but when it plays up, this drops to around 30 to 40mpg.

I know what you will say, that it's not accurate and i should be working it out per miles etc and yes, this is very true, but this is what I am seeing and it will happen a few times during a 40min journey, as I said, I am an avid watcher of the instantaneous MPG, so any big fluctuations I notice.

Another issue is, once the car warms up I can hear a dull noise, it's not really what you would call a whine but similar, it's probably close to a bike chain sort of noise, it's getting louder over time, 2 years ago it was barely noticeable, now it's deffo noticeable but would probably still need to point it out to someone else. The noise is either there or its not, and I think it starts at around 2k rpm but it doesn't change in pitch at all. Perhaps a bearing on something?

Another issue is low idle is starting to struggle, not enough to stall but it's probably getting there.

Last one, when it's cold out or damp, there's a different dull whine, it's louder depending on how cold or damp but will go away after a short time, sometimes a as short as a few seconds and other times perhaps a minute. I have heard other cars belts whine and it's not like that, it's much lower on tone, it doesn't change in pitch like a fan belt does.

These issues could all be connected for all I know and that ain't much at all lol if you've rad this far, thank you, any ideas please?