Are people driving slower to save fuel?

[old-git]

My wife, who drives to work along the A12, has noticed a marked reduction of the speed in the outside lane in the last few weeks with very few cars exceeding 70.

Anyone else noticed this?

 

[T9 man]

I noticed this also! Don't travel down the A12 too often, but I was travelling down to Abbott Racing in Wix - Manningtree last week and the outside lane in particular was not the usual grand prix circuit. This was also noticed again on the return journey some 7-8 hours later :amuse:

Silly petrol prices or police patrols do you think?

 

[HDi fun]

Definitely - I've joined in as well.

 

[obi_waynne]

Yup, this is almost certainly down to the price of petrol - it is the same down here on the South coast.

I wouln't mind betting that a car at 80mph is using 20-25% more fuel than one doing just under 70.

I save up all the saved fuel for a fun drive at the weekends.

 

[HDi fun]

Yup, this is almost certainly down to the price of petrol - it is the same down here on the South coast.

I wouln't mind betting that a car at 80mph is using 20-25% more fuel than one doing just under 70.

I save up all the saved fuel for a fun drive at the weekends.

I doubt the difference is quite that large, except possibly in the case of very small cars, say 1.0 Micra

 

[old-git]

I doubt the difference is quite that large, except possibly in the case of very small cars, say 1.0 Micra

Taken from the AA site:

Stick to the limits – Drive at or within the speed limit – the faster you go the greater the fuel consumption and the greater the pollution too. According to the Department for Transport driving at 70mph uses up to 9% more fuel than at 60mph and up to 15% more than at 50mph. Cruising at 80mph can use up to 25% more fuel than at 70mph.

 

[HDi fun]

Taken from the AA site:

Stick to the limits – Drive at or within the speed limit – the faster you go the greater the fuel consumption and the greater the pollution too. According to the Department for Transport driving at 70mph uses up to 9% more fuel than at 60mph and up to 15% more than at 50mph. Cruising at 80mph can use up to 25% more fuel than at 70mph.

The crucial phrase is 'up to'. The most efficient speed for any particular car is dependent upon many factors - gearing, torque/power profile, air resistance etc.

What is completely true though is that if you double your speed your wind drag increases fourfold. It's proportional to the square of speed.

In my practical and unscientific 'tests' I find that at 90mph I use about 10% more than at a rigid 70mph.

So, in general, slower means cheaper, if for no other reason that you're not pressing on so hard that you're relying upon incessant speed adjustment to maintain a higher speed safely.

Then again, a steady and smooth 80mph will be more economical than a haphazardly maintained 75mph.

Back to the old thing - driving style is the single biggest factor. Observation and planning rule the economy roost.

 

[Prince]

Definitely - I've joined in as well.

Even I've been doing it lately! V-Power in Northampton has hit £1.40 a litre so I can't afford to waste it atm.

 

[HDi fun]

Try the Shell standard U/L - the Fuelsave stuff suits my 528 very well indeed. If anything it's even quieter still on that than any other fuel I've tried it with - and it's not the World's loudest car by any stretch.

 

[Jakeymd]

Guilty for this. But still can't resist putting my foot down every now and then. Making all my economical driving pointless and still slow.

 

[HDi fun]

Guilty for this. But still can't resist putting my foot down every now and then. Making all my economical driving pointless and still slow.

We all do this here and there, livening up a drive by picking up the pace here and there when safe is a good way to remain alert.

I used to drive my diesel Peugeot 406 to 130+mph occasionally just to clean out the accumulated junk. This kind of speed was reserved for a local private airfield to which I have access on the basis that I have a business client located on said airfield.

 

[dpsubaru]

Taken from the AA site:

Stick to the limits – Drive at or within the speed limit – the faster you go the greater the fuel consumption and the greater the pollution too. According to the Department for Transport driving at 70mph uses up to 9% more fuel than at 60mph and up to 15% more than at 50mph. Cruising at 80mph can use up to 25% more fuel than at 70mph.

Think that the Dep of Transport shuold come and test my Subaru, dont know what is it about them but fuel consumption seems to be the same regardless of the way its driven - not obviously taking it to the extreme, but sticing the foot down hard whenever getting the chance to etc. Always 300milles (give or take a couple) to the tank.

on topic, everytime i come back to the UK (am away for 6months at a time) the traffic does seem to be moving slower. And the amount of people really hounding it down the outside lane has really dropped.

 

[obi_waynne]

I think in highly tuned cars there is little difference although there is a big power requirement to overcome the wind drag. If a car is aerodynamic already then it will probably make very little difference, nearer 5-7%.

The powerful engines are running fairly efficiently and at quarter or half throttle load there is not much to be gained.