Some people would love to be able to drive at 56mph commuting to work. Most of the time it's 10-20 stop start!

Although I do drive at 70 on motorways, I would be more than happy to drive at 56mph if I could get there without delays. I'm not sure how prevalent that view is though - I can't imagine white van man, boy racers and company car drivers who live in their cars agreeing.

On a slightly separate subject, I would introduce a noise element to the VED tax - no noise = no premium; boy racer/4x4 noises would add premiums. So we could have a double benefit... improved fuel economy at 56mph and improve environmental stuff (less noise and other pollution).

Will I need to call in the grim reaper soon?

Some threads are being introduced off subject.

Perhaps we should start an offshoot forum on green living? I'm happy to discuss this till the cows come home but on a green building forum people will expect a tight ship or the captain might be keelhauled.

I've recently discovered a sixth gear on my Audi... its called neutral and I use it for all down hill sections and for coasting up to junctions. I'm not sure that this is good driving practice but it's pushing the mpg up.

Posted By: Chris WardleI've recently discovered a sixth gear on my Audi... its called neutral and I use it for all down hill sections and for coasting up to junctions. I'm not sure that this is good driving practice but it's pushing the mpg up.

It's not just not good practice, it's dangerous and illegal and doesn't save any fuel. According to the highway code, you should be in control of your vehicle at all times - coasting in neutral is not being in control. It's especially dangerous going downhill as you may find the lack of engine braking overheats your brakes - I was in a car that this happened to (as a passenger) and I can tell you that was the last time that idiot driver ever coasted down a hill.

As for saving fuel, you'll use more fuel when coasting, not less. Since fuel injection and engine computers became standard features, all fuel injection is shut off if the car is decelerating whilst in gear - i.e. zero fuel consumption. If you coast, a small amount of fuel will be burned to keep the engine turning at idle speed.

Seriously, do not ever consider coasting - it's not economical and it is illegal because it is dangerous.

Paul in Montreal

p.s. and as for driving speed, I think there should be no limit except where dictated by safety considerations. If the speed limits were increased, the capacity of the roads would increase and this would probably lower overall fuel consumption, not raise it. If I do a cost benefit analysis of the differential cost of extra fuel used due to driving faster, I find it is always much less than the value of my time at the standard rate I bill clients. The cost I pay in taxes is directly related to my consumption (and hence also to CO2 emissions) so there's no need for any extra taxes - we already have de facto carbon taxes on fuel usage. It's up to me how I use that - sometimes I drive slowly and "economically" and sometimes it's more economic for me to drive fast - especially here in the Great White North where the roads are virtually empty - even between major cities

Ah... better pack that in then

Posted By: Paul in MontrealIf the speed limits were increased, the capacity of the roads would increase and this would probably lower overall fuel consumption, not raise it.

I think you will find that the capacity of a road actually reduces the faster the speed limit is. This is because the faster you drive the greater the stopping distance and the greater the gap needed from the car in front.

The most important aspects of eco driving are driving smoothly, change up early and plan ahead to avoid unnecessary braking.
I think that the current speed limits, if adhered to, are about right.

Posted By: (GBP) KeithWill I need to call in the grim reaper soon?

No, 50 is still quite young. Encourage folk to use descriptive thread titles then if you don't care about topics such as "How fast should we drive?" you can esily skip it without wasting your time.

Surprisingly, it was the green anti-christ Jeremy Clarkson who alerted me to the fact that you get zero fuel consumption when travelling in gear and decelerating.

He was attempting (and succeeded) in driving from London to Edinburgh and back on a single tank of fuel in an Audi something or other a while ago.

I always used to coast, but have noticed a marked improvement by just cruising down hills in 6th, and up to red lights.



so there you go

What's this about reducing the speed from 70 to 56? Have you ever driven on a motorway at bang on 70? Almost everyone passes you, except for lorries, caravans and old people who drive at 60 in the middle lane! Getting everyone to drive at 70 instead of 80 or 90 would be a good start!
I kind of think it a public duty to stick to 70 as it can reduce the person behind you's speed, thus saving them money too.

The 70 max campaign has interesting thoughts on this: -
http://www.70max.com/

Mark

I was thinking along those lines myself, buildexpress. Can you tell us more, e.g. how much is costs, where the tank goes etc?

Current car (Audi A4, 1.8 petrol) has done 150k miles but seems to be going well enough. Not sure whether a gas conversion would pay if the engine will perhaps only stand another 30k or so and I'm loathed to part with what has been a reliable motor but which, due to the mileage, has negligible resale value.

to Chris Wardle request.....
I decided to convert when the tax on larger cars was to be increase. Lets face it, I drive a Jag X type 2.5 Petrol, who would want that with the petrol and tax so high, and again petrol will never come down in price, now it is this high.

The government are making so much money in tax "as they would say if it was a private company - wind fall tax".
So i decided to bite the bullet, the cost was £1500.00 and I accepted that this has gone, but a recover the cost each time I fill up or the cost of fuel increases.Its a great feeling, filling up for £30.00.

The Jag has now a resale value, it cost me less to run than a mini? but I am going to keep it, unless I win the Lottery

Posted By: TheDoctorSurprisingly, it was the green anti-christ Jeremy Clarkson who alerted me to the fact that you get zero fuel consumption when travelling in gear and decelerating.

I believe that's at least partly correct. The injectors on a modern car can indeed shut off completly when coasting ingear but they can't when coasting in neutral. However I wonder if the drag of the engine allows you to coast as far in gear as it would in neutral? Perhaps the drag of the engine slows you down more so you have to accelerate harder to regain your desired speed.

Generally driving at a constant speed works best because drag is proportional to the square of the speed and power required is proportional to the cube. Say you want to average 60mph and you drive half the time at 50 and the other half at 70.. the bit you save by driving at 50 is less than extra you burn by driving at 70. So a constant 60 is better.

Paul

I am having difficulty understanding what you are saying. On the one hand you are saying that the faster you go the greater the road capacity, but only if there is no congestion.
If there is no congestion no one cares what the road capacity is anyway.

The M25 western section uses speed management to maximise the capacity of the road and improve flow. Prior to this the road was almost gridlock with stop start traffic trying to go as fast as possible. Speed management in these conditions is good for fuel economy and good for easing congestion.

I dont think I have ever experienced congestion because the speed limit is set too low.

The average traffic speed in London according to Citroen is just 7 mph and we blame the speed limit for it.