Why is a new Fiesta more fuel-efficient than an old one?

WobblyDog

I'm considering replacing an old Fiesta with a new Fiesta, and I'm puzzled why the new one has much better official fuel consumption figures:

1998 1.25 manual petrol Fiesta (75PS):
31.7mpg (urban), 50.4mpg (non-urban), 41.5mpg (combined)
Measured according to" EEC 80/1268/EEC (version 93/116/EEC)"
Axle ratio:4.27
Hydraulic power steering
Kerb weight 1055kg
(from handbook)

2011 1.25 manual petrol Fiesta (82PS)
38.2mpg (urban), 62.8mpg (non-urban), 50.4mpg (combined)
Measured according to "80/1268/EEC or the European Regulation (EC) 715/2007 amended by (EC) 692/2008"
Axle ratio:4.07 (I think)
Electric power steering?
Kerb weight: 1041kg
(from websites)

These 2 cars are based on the same engine, although presumably a lot of tweaks have been in the intervening 13 years.

Can the improvement in efficiency be explained by the longer gearing, engine tweaks and better aerodyamics? What else have the manufacturers done to achieve this?

The EEC regulations governing fuel consumption measurement seem to have changed in this period - can direct comparisons be made between these fuel consumption figures?

The_Loan_Ranger

You'll find that there have been many improvements made since 1998; the engine will not be the same unit, despite being advertised as a '1.25 petrol manual' ; Zetec? In 1998 it may well have been an 'Endura', though suprisingly, this was more economic than the Zetec.

Despite engine modifications, the way it's been tuned, aerodynamics etc (as you've already suggested) will have created these changes.

zappahey

Lots of little tweaks here and there including the few kgs that it has lost, electric power steering and improved electronics for the fuelling. It all adds to efficiency.

forgotmyname

It produces more power from the same capacity, So more efficient. Lighter weight and better aerodynamics go slightly
towards the better fuel consumption.

Wonder why it has more power and lighter weight yet takes longer from 0 - 60. Gearing is so tall you can only achieve
the figures mentioned on empty roads with a following wind or indoors on a rolling road.

The driving cycles are usually done that way so traffic and traffic lights and hills etc do not come into it.

American manufacturers got their wrists slapped any years back. Quoting a car had 300bhp when it did not. The engine
could produce 300bhp on a workbench with no fans or pumps running and a special extractor exhaust. But when fitted into
the car could easily lose 50bhp.

motorguy

Just as an aside, i was reading in this months What Car? that due to the advances in fuel consumption like those above, in real terms, people arent paying any more for fuel than they were ten years ago, as although prices have went up, economy has also went up - that of course is assuming you're talking about a 10 year old car and a new car now.

Kilty_2

pgilc1 wrote: »

Just as an aside, i was reading in this months What Car? that due to the advances in fuel consumption like those above, in real terms, people arent paying any more for fuel than they were ten years ago, as although prices have went up, economy has also went up - that of course is assuming you're talking about a 10 year old car and a new car now.

Great - bet the Government can't wait to get a hold of that.

Hammyman

I've been saying it for ages. As a percentage of income, fuel costs no more than it did decades ago.

MX5huggy

Progress what progress, Autocars 1st road test was an Austin 7 in managed 42.4 mpg in 1928.

Derivative

I'm not sure if this is indeed your reason for upgrading, but remember that at current petrol prices you'd be able to buy something like 70000 miles' worth of petrol for the old car before you make up the cost of the new model.

Strider590

Newer cars are bigger and heavier, have more power etc etc

The 1.25 has always been a Zetec, the differences will be in the way the engine management runs, it'll be tuned to give great MPG during testing conditions, but out in the real world it'll be no better than in 1998.

notafan

Looking at the weights you listed looks like the Mk7 (1055kg) is also lighter then the Mk4 (1055kg) model you list so again that helps it along.

Plus the engine tech - i'm not upto spec on ford and also the engine has come on from zetec to duratec although i believe they are sometimes refered to as the same - either way i'm sure its a different engine in the new one, and it'll have had tweaks since the previous model too.