'Petrol efficiency experiment; an increase of 20%' blog discussion

pault123

Tojo_Ralph wrote: »

So here are my driving home figures with the tunes cranked up. I didn't really get the traffic and had to gun the car a couple of times to pass slow moving vehicles.

To... Ave 41.5 mpg... Ave Speed 23 mph... 31 mins... 11.5 miles. Tunes On
From... Ave 46.3 mpg... Ave Speed 32 mph... 21 mins... 11.5 miles. Tunes On

To... Ave 42.8mpg... Ave Speed 22 mph... Time 31 mins... 11.5 miles. Tunes Off
From... Ave 50.4mpg... Ave Speed 34 mph... Time 20 mins... 11.5 miles. Tunes Off

That said, I don't trust the figures at all and just know that when I fill the tank and do the sums I'm going to see an average of 40 mpg, which is well down on the 51.3 mpg published Ave Combined. I'll wait until I get more miles on the clock before drawing conclusions.

Some good research there! :beer:

May have to carry some tests out myself lol

my x8 speakers are only powered by the headunit as far as I know so a bit less of a power drain than 10 amps! :eek:

Tojo_Ralph

pault123 wrote: »

my x8 speakers are only powered by the headunit as far as I know so a bit less of a power drain than 10 amps! :eek:

I am no audiophile, but I assume the amplifiers are small ones and have something to do with the DSP which converts two channel stereo signals into 7.1-channel surround sound or they are needed for the intelligent loudness system that makes sure the bass, treble etc are as set? .... I think what we really need an audio geek.

steve6375

tomstickland wrote: »

I've done a lot of thinking about this. I don't think that cautious acceleration helps much - if you wish to accelerate from 20 to 60 then it will take a certain amount of energy to do so, and doing it in 15s versus 45s doesn't make a huge difference.
However, it is throwing energy away by braking that is where the savings can be made.

yes, moderate acceleration only uses 'slightly' more fuel than mild acceleration.
Actually, it is driving with your foot off the accelerator that saves the most fuel as you are travelling at over 100 mpg (actually nearer 200mpg on many cars). So the difference between 40 mpg and 20 mpg is not really significant compared to 200 mpg!

So take your foot off the pedal whenever you can and then accelerate back up again when you need to. This will save more than granny driving.

pault123

steve6375 wrote: »

yes, moderate acceleration only uses 'slightly' more fuel than mild acceleration.
Actually, it is driving with your foot off the accelerator that saves the most fuel as you are travelling at over 100 mpg (actually nearer 200mpg on many cars). So the difference between 40 mpg and 20 mpg is not really significant compared to 200 mpg!

So take your foot off the pedal whenever you can and then accelerate back up again when you need to. This will save more than granny driving.

The actual official name for this is Pulse & Glide see my post here >>>

http://forums.moneysavingexpert.com/showthread.html?p=11715407#post11715407.

mark55man

Thanks pault123 very interesting. have responded on your referenced thread, and whilst it may be hard for many peopelk to find the circumstances to use this effectively, I may be one of the lucky ones !!

Regards

martinp79

bigpat wrote: »

I haven't read all eight pages of this thread, but does anyone else use neutral rather than potentially wearing out their clutch for "coasting"? I've only been doing this for about six weeks now and already i'm seeing approx 15% extra mileage out of my tank of diesel (2.0L Vectra 04 reg).

If I'm on the dual carriageway and traffic is light, I will smoothly get my speed up to about 70 and then pop it in neutral. The rev counter drops back to idle speed, but my speed stays the same for ages. I've travelled nearly a mile before my speed goes under 50 and other motorists are free to overtake if they wish. Equally, even around town, I've started to think ahead more and if I see I'm going to come up on a queue of traffic or if I need to slow for a roundabout or stop at a give-way, I'll slip it out of gear in good time.

All the while being MORE aware than I ever was before of what's in my rear-view mirror, so that if I need to speed up I can put it back in fourth or fifth, depending on what speed I'm coasting at.

And if I should come to the top of a steep hill, then I just need to nose it over the top and gravity will do the rest.


Last week I even overtook someone while I was doing sixty in neutral. It felt just great knowing that I was probably burning less fuel than he was. Two minutes before that I'd been overtaken by some nutter doing at least 100, and then watched his brake-lights light up as he approached the roundabout. I reckon he got to it maybe five seconds before I did and then I could hear his engine over mine as he floored it again. I bet his journey cost a lot more than mine for a few seconds spared.

I haven't tried any of this on a motorway yet, as it's generally rush (crawl) hour, so you don't get much momentum in the first place.

I learned a lot of this stuff during the 2000 fuel strike. We had just arrived in Cornwall for a weeks holiday from the midlands and had planned to drive about a bit. We knew we needed half a tank to get home, so we drove VERY sparingly while we were down there. And we noticed most other drivers wewre doing it too. I recall dawdling along at 40 in the inside lane of a dual carriageway and even though traffic was reasonably heavy, almost no-one was overtaking.

Ever since then I've stopped thinking about miles per gallon and instead measured it in miles per tank. And recently I have consistently got well over 500 from my tank, sometimes 520, whereas it was always under 450 before.

And now, my thinking has moved on again, to "miles per pound". I worked out a few months ago that (on average) every eight miles I drove cost £1. But now I'm sure I'm getting well over nine and possibly ten. It will need to be averaged out over a few months though.

Cycling and walking help too!:D

There's a couple of points here:

(1) I don't think depressing the clutch wears it out as its not causing extra wear, holding a car on a hill start using the clutch or traffic jam stop start driving would wear the clutch as it should be the bit in the middle that wears it most (but I'm not a mechanic, so could be wrong, it just seems like common sense)

(2) The ECU may cut off the fuel, but as people have mentioned it is 'engine braking' - clutch depressed or neutral, the car will coast further than with the car in gear. I have a couple of straights that I can coast along without losing momentum.

Incidentally, what is classed as a modern engine? I have a 2000 mk4 astra diesel and a 2001 mazda premacy petrol.

Great discussion. Normally, by the time I get to 1/4 tank, I've only done 300 miles, I'm now on 410 and still hovering above.

MoochyMoMo

I have been doing this Petrol efficientcy for the last couple of months and it really makes a difference. I thought that sticking to 60 on the dual carriageway would be a nightmare but I let everyone pass me by with a smug thought in my head that my fuel will last longer. And I thought it would take me longer to get to my destinations but there is no difference at all which is very handy to know. As someone currently looking for work and without an income I have to economise on everything and have signed up to the website suggested so that I know where the cheapest fuel is in my area.

I drive an economical car anyway (Fiat Siecento) and have managed to gain approx 60-80 more miles out of my fuel tank.

laurajd28

Hi,

Does anyone have a Ford Sport KA?
I only had mine last Friday, and have already put £70 in petrol in it. £25 fills it to half, and I haven't filled it full yet as I don't want to be driving around with the extra weight of fuel.

I went to work 2 times in it (total of 180 miles on the dual carriageway), and around town and did 250miles on £25 worth of petrol which I suppose isn't too bad (about 37mpg). But then I went to work in it again (90 miles), and about 50 miles around town and only did 140 miles (even though I put £25 worth of petrol in it again).

I'm going to try some of the tips that I've read on here - taking my foot off the revs, keeping off the brakes, slower acceleration etc... and see if that helps.

Has anyone got any tips for me or had any experience of driving a sport ka?

Thanks

merlie

... so I've been doing the test on a few tank fulls of fuel and I have manged to get my previuos personal best of 34mpg up to 47mpg.
What I've been doing is using the accelerator like a "thruster" hitting the accelerator every now and again to maintain a cruising speed.... ok it sounds daft but it really works. Then theres the mental game of looking way ahead to avoid hitting red traffic lights and avoid waiting on entry at roundabouts for gaps. By my calculations I save roughly £16 per tank full and about £370 per year !
Journey times arent vastly different ...
Anyone elsy noticed that motorway traffic is more leisurley these days ? I dont do too much motorway miles but there are a lot less vehicles doing 90+ than there used to...

scape

merlie wrote: »

What I've been doing is using the accelerator like a "thruster" hitting the accelerator every now and again to maintain a cruising speed.... ok it sounds daft but it really works.

I don't believe this will save fuel - in fact, quite the opposite. Considerably more fuel is used when accelarating up to a speed than decelerating with your foot completely off the gas. So on-gas, off-gas, on-gas, off-gass (even subtly) will use more fuel than gently hoding the gas at a point which keeps the car at a certain speed. On a side note, this style of driving may also be uncomfortable for passengers.

merlie wrote: »

Then theres the mental game of looking way ahead to avoid hitting red traffic lights and avoid waiting on entry at roundabouts for gaps.

Now this does work - for exactly the reasons I pointed out above. This 'method' will have a greater effect than your above thrusting method; hence you're still getting a saving.

merlie wrote: »

By my calculations I save roughly £16 per tank full and about £370 per year !
Journey times arent vastly different ...

Try focussing only on driving attitude and not 'thrusting' - see if there is even more saving!

merlie wrote: »

Anyone elsy noticed that motorway traffic is more leisurley these days ? I dont do too much motorway miles but there are a lot less vehicles doing 90+ than there used to...

not really! Maybe less people are caning it down the motorway because travelling at 90+mph compared to 70mph uses vastly more fuel than you would expect. Come to think of it - you may be right. I've been driving for 5 years now - when I first started, fuel was 72.9p/l - so maybe thats the reason why.