New car mpg

20aday

After driving Unleaded motors for the last seven years (Rover Metro followed by a Ford Fiesta MK5) I've just switched to a Fiesta MK6 (Zetec Diesel) and I find it gets warm in around five minutes or so.

There's a heater setting to warm the interior quickly which is a bonus given our current weather!

In terms of economy I'm average 57mpg (using the inbuilt tripometer) but my (combined) mpg should be 68.9 according to my manual.

bowlhead99

20aday wrote: »

In terms of economy I'm average 57mpg (using the inbuilt tripometer) but my (combined) mpg should be 68.9 according to my manual.

It's always a bit funny when someone says my mpg should be x mpg.

Your Combined mpg might well really be 68.9, even if you've never seen results that good, because that is a defined term, being the average from the official Urban and Extra-Urban tests, carried out to the EC rules in a lab.

Presumably you haven't actually run those tests, travelling the specific speeds and distances with your heater and stereo and aircon and lights turned off, zero traffic and with as much as possible jettisoned to save weight. Under those conditions, maybe your car could do it. Over those two tests 'combined' you would just cover about 11km in about 20 mins, so average about 20mph, with max speed of about 75mph for one minute. But if your driving is anything not like that, you won't get results like that.

As a rule of thumb, it sounds like your driving style gets you about 83% of the official figures, so maybe that percentage would hold true against official figures if you changed your Fiesta for something different from another manufacturer. Of course, some cars are engineered for stop-start round town and some for effortless cruising at low revs on motorways and your own driving will be somewhere in between those poles.

So your exact same 'usual' journey on another car might really suit that car, or might really not, so your real world mpg in another car may or may not be over 80% of what it 'should' get on the Combined test.

20aday

bowlhead99 wrote: »

It's always a bit funny when someone says my mpg should be x mpg.

Your Combined mpg might well really be 68.9, even if you've never seen results that good, because that is a defined term, being the average from the official Urban and Extra-Urban tests, carried out to the EC rules in a lab.

Presumably you haven't actually run those tests, travelling the specific speeds and distances with your heater and stereo and aircon and lights turned off, zero traffic and with as much as possible jettisoned to save weight. Under those conditions, maybe your car could do it. Over those two tests 'combined' you would just cover about 11km in about 20 mins, so average about 20mph, with max speed of about 75mph for one minute. But if your driving is anything not like that, you won't get results like that.

As a rule of thumb, it sounds like your driving style gets you about 83% of the official figures, so maybe that percentage would hold true against official figures if you changed your Fiesta for something different from another manufacturer. Of course, some cars are engineered for stop-start round town and some for effortless cruising at low revs on motorways and your own driving will be somewhere in between those poles.

So your exact same 'usual' journey on another car might really suit that car, or might really not, so your real world mpg in another car may or may not be over 80% of what it 'should' get on the Combined test.

Thank you for replying. I'm well aware the quoted figures won't "apply" to real-world figures as I know the numbers quoted in any form of advert/manual are conducted in lab. conditions.

In fact I'm very happy with the figures I'm returning so far; I *could* possibly get it slightly higher if my daily commute to work wasn't frequented by traffic lights and varying speed limits/other people on the road.