Hi all,

Firstly I'd like to say I have been lurking on these forums for a little while now and have found many topics on here to be interesting and full of great information, so I thought I'd leave this here and see what responses I get.

So I just did a service on my car myself (oil, air & and fuel filters) and took it for a test run to make sure it was all good and I was getting good MPG, 60-65 throughout my 20 mile run, I then parked up at Tesco and brought some bits from there. I made a phone call for an hour and a bit whilst charging my phone and battery warning eventually came on saying power save active.

I proceeded to leave and travel home and I flicked my MPG guage back on the screen and noticed it plummeting downwards even though I continued driving conservatively. I joined motorway and set cruise control to 65 and monitored my mpg. It was averaging 35-40 which was very poor for what it was previously. I thought it may be from car warming up as I was sat there a long time, but when car was at temperature it maintained the same poor economy.

The turbo spooling bars that I can get up on my dash showed 4 bars continuously up which I thought was too many for that driving. Car seemed to accelerate as it should. MPG just wpuld not go above 45 though. I was beginning to think of pulling over after 10 mins of this as something just was clearly not right ... and then out of nowhere, my MPG shot up to 65-70 and 2 bars on the turbo dropped off.

Is this something to do with charging the alternator as the battery got so low when I was parked up or is this some sort of DPF cleaning?? Thing is it started when engine wasnt even up to temp. Gave me a bit of a scare as I have only owned the car 2 weeks and I have been used to the excellent MPG it usually provides!

If anybody could clear this up thatd be seriously appreciated!