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

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  • charlieheardcharlieheard Forumite
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    When I drive I aim to not have to use the brakes, I find this helps greatly, you are always consious of your speed because you have to think ahead, you tend not to drive too close to the car in front, you are constantly aware of the need to slow down at junctions etc and you save on wear to the braking system as well as becomming more confident and calm.
    I agree wholeheartedly with being aware of your surroundings and avoiding using the brakes: I try to do the same. Have you seen those people on the motorway whose whole journey seems to consist of accelerating close to the car in front and then braking hard while I haven't touched mine for miles. :rolleyes: Clarkson said something similar on Top Gear last year.

    A quick counterpoint though: brake lights are a warning to cars behind, so using your brakes to illuminate the lights is useful even when you don't actually need to brake yourself. Also repeated engine braking can cause wear to the engine, so should be used moderately (as I'm sure you do) instead of as a replacement for brakes. My driving instructor said, "Which is cheaper to replace: brake pads & discs or a whole engine?"
    Jumbo

    "You may have speed, but I have momentum"
  • kaya wrote: »
    you cannnot accuratley judge fuel efficiency by volume guys and gals, sorry, petrol increases and decreases in volume according to its temperature, the only way to accurately judge fuel economy would be to weigh the fuel in the tank before and after the test period, trip computers in cars arent too good either, putting a different set of wheels/tyres on your car can make a huge difference to the reading also as your changing the outer circumference of the wheels

    Providing you are using normal retail outlets that store fuel underground, which reduces temperature variation, and fill up at the same time each day and at the same time of year you would struggle to get a difference of 0.25% in mass of fuel delivered due to temperature related volume changes.

    Probably accurate enough for the purpose of this experiment.
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  • anewman wrote: »
    Easter is not to celebrate his death but his rising from death.
    He died on Good Friday not Easter Sunday (when we have the Easter eggs)!

    Re. the petrol saving discussion. I always drive taking my foot off the accelerator when approaching roundabouts etc. and am constantly amazed at the number of cars bombing past me and then slamming on their brakes at the last minute. Some also brake at any changes ahead such as a slight curve in the road, cars way in front of them and even traffic coming in the other direction. I believe they think that they either have to have their foot on the accelerator or brake, such a waste of petrol!
  • reduxredux Forumite
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    Errrm, a slight mathematical difference about what Martin said:

    Going 20% further on a tankful means the rate of consumption, and hence the cost of a fixed length trip or of all fuel bought, drops by 16.7% not 20%

    To make the point clearer by stretching things, going 100% further on a tankful is a 50% cost saving

    Many countries define fuel consumption in units that are reciprocal to the way we do, e.g. in litres per 100 km, and maybe that's why
  • MushyPeasMushyPeas Forumite
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    Interseting post as I've been thinking a lot about fuel consumption. I travel a lot between SWest and London. I noticed that if I took the motorway my consumption increased (driving around 70 mph) whereas on the 'old road' up it was averaging 60mph so was more fuel efficient.

    Also I purchased a tomtom last year. I keep experimenting with the 'shortage' route versus the 'fastest' route. Sometimes the time different isn't much but I save around 5 miles in distance. Though in the country you do end up going down some little roads! Has anyone else tried this method to save mileage?

    My next plan is to calculate how much it costs me to drive a mile, will get around to that soon :grin:
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  • SkeksisSkeksis Forumite
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    I have 'experimented' this week by driving more sympathetically and carefully than I normally would and although I don't have a fuel consumption readout on my car, I have found that I haven't used as much fuel as I normally would in a normal working week!

    I fill up at a BP garage which luckily has to price match with an Asda station over the road, otherwise it would be out of business!
  • redpeteredpete Forumite
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    anewman wrote: »
    and also driving at the speed quoted by your car manufacturer as having the best MPG, usually about 56mph, instead of 70 or 80mph on the motorway.

    56mph is often quoted because this is a standard used to give a common comparison point, it is not the speed at which cars exhibit the best mpg.
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  • For info, this is also being discussed over on the Advanced Driving UK site at
    http://www.advanced-driving.co.uk/bb/viewtopic.php?p=29301#29301

    Some interesting tips on fuel economy http://www.advanced-driving.co.uk/driving-tips/put-the-car-on-a-low-fuel-diet-for-2008/

    You might also find the fuel economy spreadsheet useful to calculate your own fuel ecomony
    http://www.advanced-driving.co.uk/public/fuelecon.xls
  • charlieheardcharlieheard Forumite
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    MushyPeas wrote: »
    Interseting post as I've been thinking a lot about fuel consumption. I travel a lot between SWest and London. I noticed that if I took the motorway my consumption increased (driving around 70 mph) whereas on the 'old road' up it was averaging 60mph so was more fuel efficient.

    Also I purchased a tomtom last year. I keep experimenting with the 'shortage' route versus the 'fastest' route. Sometimes the time different isn't much but I save around 5 miles in distance. Though in the country you do end up going down some little roads! Has anyone else tried this method to save mileage?

    My next plan is to calculate how much it costs me to drive a mile, will get around to that soon :grin:
    I'm very surprised that your consumption is higher on the motorway unless you're travelling significantly faster than 70mph. One thing that really kills fuel consumption (apart from high speed) is changing your speed. Slowing down for corners and junctions and speed limits around towns all mean that the car using energy to return to the cruising speed. So as well as being slower, non-motorways usually mean poorer consumption. Think of it like going the shortest route on a walk. You lose loads of time and energy climbing hills and descending rather than taking the smoother, longer path.

    It also means that the shortest route is seldom the most economical, as it usually involves lots of junctions and minor roads. (Unless you're travelling on a bicycle, of course, where the cruising speed isn't very high, so distance is more important than cruising. ;))
    Jumbo

    "You may have speed, but I have momentum"
  • I seen a product in the garage called Redex which is reputed to save up to 20% of petrol when it is put in the tank.
    Does anyone know if this stuff works?

    Lynne. :confused:
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