Hi,

This question relates to two separate events, both of which reduced the mpg quite a lot.

First - I did a routine service last month; oil, oil filter, air filter. Afterwards my average went down from (about) 48 to 44 mpg.

Second - I had to fit a new battery last week. Economy has now dropped to 40mpg.

Any thoughts?
Thanks, Andy

 

Guess you have the diesel. When I got my 2007 2.0 manual I was getting around 30 but the more miles I put on it I'm now trending towards 28. Either I'm driving faster or it's wearing out. Also don't trust the computer, mine fluctuates by about 5 mpg average up and down.

 

Hi Byrun,
Yes - it's the 1.9 diesel.

I agree with you that it's reasonable for the mpg to drop off with time (and my car has over 140k miles on the clock), but these events are sudden.

I've confirmed the change by measuring miles between fuel fills. I do the same journey from North Wales to the Lake District and back every week; mostly during the night so speeds are constant, so it's quite easy to compare.

I was wondering if the ecu fuelling map reverts to its default after removing the battery - in which case the mpg should recover slowly as it re-learns the optimum settings for my car?