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

RichS_2

I recall an episode of top gear where JC said, if you allow the car to slow down into a junction while in gear, rather than put the clutch down and coast into it this burns no fuel at all.

In this case, if you have a journey that is downhill all the way and you cruise down in gear without accelerating this will use no fuel. Anyone with a trip computer able to confirm this?

RichS_2

Just found an example in an earlier quote about how engine braking cuts off fuel in modern cars (see last paragraph in EcoDriving article below).

So, to repeat my question for those of you with a trip computer: does continual engine braking (eg traveling downhill) eliminate all fuel use?

pault123

Managed to increase my mpg by 4mpg with eco driving. Now getting 34 mpg, which for my 1995 1.4 golf is actually pretty good. 0.14p a mile its costing me.

I fell kinda :mad: when I hear about some of you guys getting 60-75mpg!

If I could get a 60-75 mpg diesel in theory my fuel spend per month would be half, ie £70-£80 a month better off . ie, £70-£80 a month towards a 1.6 TDi VW.

Good idea/bad idea?

charlieheard

RichS wrote: »

Just found an example in an earlier quote about how engine braking cuts off fuel in modern cars (see last paragraph in EcoDriving article below).

So, to repeat my question for those of you with a trip computer: does continual engine braking (eg traveling downhill) eliminate all fuel use?

Trip computer's usually cannot say if you're using no fuel, as they do miles per gallon - using no gallons means the result is either infinity (or a very large number). What they do (in my experience) is "max-out" at some reading like 99.9mpg. I regularly get that reading when slowing for a junction.

Engine management systems will turn off fuel supply when certain criteria are met - so as long as the revs are high enough (more than 1500-2000 rpm) and the throttle is closed, it will stop the fuel supply. It will restart using fuel when the revs drop to keep the engine running smoothly. Of course, if you use an full automatic, you lose a lot of that benefit.

beaker141

To the guy with the thirsty radio - try having the radio on but turned to zero volume and see what happens ?

torbrex

A wise man once told me the two main controling factors for fuel economy are:
1 - The time that you leave your starting point.
2 - how heavily you press each of the pedals that your right foot comes into contact with
From this, I always try to leave at least 15 minutes earlier than the journey should take me and try to avoid both heavy braking and heavy acceleration, I try to keep my speed as constant as possible and tend to cruise at 55.

My current car averages 45 mpg in all driving and 60 mpg when on trips of 100 miles or more.

Rexy

setmefree2 wrote: »

Hi

Me & Mr SMF are trying really hard not to use our car at all. We have a Scenic. The problem with this is that often the battery goes flat through lack of use and we are continually having to recharge it. We have bought a solar pannel which tries to get it "juiced up" but does anyone have any other ideas or share our problem We can't live without a car completely.:rolleyes:

Any battery benefits from not being connected to retain a charge, even if the device is switched off.

So you could actually disconnect one of the battery terminals, and see if that helps matters.

My father suffered from the same problems, but it is better now as he uses the car at least once a week.

On another point, when I lived in London (good public transport admittedly), I sold my car, cycled to work, walked to the shops and got a Taxi back with the supermarket shopping once a week. We hired a car on the odd occasion we needed to travel distance, but that generally still works out cheaper than train fares.

charlieheard

Rexy wrote: »

Any battery benefits from not being connected to retain a charge, even if the device is switched off.

So you could actually disconnect one of the battery terminals, and see if that helps matters.

Be wary of disconnecting the battery on modern cars. At least you will have to enter the radio code - do you know what yours is? Plus it occasionally can upset the immobiliser if you have one - most modern cars do.

A better way of maintaining the battery is to get a trickle charger, which will automatically keep the battery topped up. You can even put it on a timer so that it only runs an hour a day. That's what I've done with my classic car (amongst other thing) as it doesn't get used much in winter.

Cars should be able to hold their charge under normal conditions for over 2 weeks - it may be less in very cold weather. If it's regularly failing to last that long, there may be a problem with the wiring. The only issue is that these problems are notoriously hard to identify :rolleyes:

Cars don't "like" being left idle: seals dry out and rust forms on brakes and even inside the engine if left long enough. Much better to use it regularly - so you could do everything on a Saturday: major shop, trips to the tip/allotment/relatives. This is better than leaving it, but also better than just using it willy-nilly like we all tend to without thinking.

Rexy wrote: »

On another point, when I lived in London (good public transport admittedly), I sold my car, cycled to work, walked to the shops and got a Taxi back with the supermarket shopping once a week. We hired a car on the odd occasion we needed to travel distance, but that generally still works out cheaper than train fares.

We did much the same when we lived in London - the car sat outside during the week as we both cycled 12-15 miles each way to work. Quicker than taking the train or car, and much healthier. Also we just shopped locally and regularly on the way home, carrying most things in a rucksack. We did keep the car for escaping at weekends, though...:o

mark55man

bump - as ever Martin is ahead of me. I just saved £50 this month through more careful driving, at a cost of 5mins added to my trip and a benefit of getting to work substantially chilled. I do 60 miles return trip on good single carriage way A road.

£50 per month for 10minutes a day = £50 for 200 minutes = £16 an hour - when I compare to some of the other stuff I do for MSE reasons that is gold dust

beans

Driving in too low a gear is essential for optimum fuel efficiency.
Far too many people drive in too high a gear causing the engine to labour, which is inefficient. A labouring engine is audibly different from a normally running engine.

In the absence of a fuel mileage computer, a good start is to change up before 2,500rpm (petrol) and 2,000rpm (diesel).

One of the most difficult skills is driving smoothly. This is looking ahead and matching your speed to conditions. Timing your arrival at obstructions, roundabouts and lights. It is perfectly clear that many motorists have never leaned to drive smoothly. Driving smoothly will save you money and make you a safer driver.

Correct tyre pressures - saves ~ 10% fuel and makes tyres last longer. For those with low-profile tyres, correct inflation may prevent serious damage to expensive alloy wheels. Under-inflated tyres can roll off the wheel with a bang, destroying the tyre and the wheel, this is often misinterpreted as a blowout..

Tracking - if the tracking is out, your fuel is wasted destroying your tyres, while handling is impaired.

Drive slowly over speed humps - tracking.

Walk or cycle for short journeys. Engines are inefficient for short journeys. Catalysts also do not work until working temperature is reached. Walking and cycling are good for your health. Cycling is ten times as likely to extend your life as shorten it. Cycling is also great fun.