DiGuru said:
Originally Posted by mjtdevries
* aggresive driving.
They are wrong about the reason it takes more fuel. Accelerating fast isn't all that bad for fuel consumption. You are just creating potential energy that you later use when coasting. The effect on fuel consumption is minimal.
No. While you do create kinetic energy, you do so by burning about fifty times as much fuel as when cruising (see page 1 of this thread). Accelerating slowly takes longer, but is much more fuel efficient, and creates just as much kinetic energy.
No, not true.
First of all, you do not burn fifty times more.
Second, when you acceleratie slowly you burn twenty-five times more, and then do that twice as long. In the end you have used the same amount of extra fuel.
It's actually very simple. You need X amount of extra energy to get your car at the higher speed.
A liter of fuel contains Y amount of energy. So you can calculate how much fuel you need to burn, to get the extra amount of energy.
You can then choose to add that energy quickly or slowly. And that results in quick acceleration, or moderate acceleration. In both cases you need to add the same amount of energy.
The only difference is that with quick acceleration you will reach your higher speed sooner. Since a higher speed takes more fuel than a lower speed, you will use extra fuel during the amount of time the slower accelerating car hasn't reached that speed yet.
So the REAL difference between fast en slow acceleration is the difference between travelling at a higher or lower speed.
Since accelerating actually takes VERY little time during a normal trip, that difference will be even less. The actual amount of fuel savings will thus be very VERY small.
Quote:
The real fuel consumption killers are your brakes (strange as it may sound)
When you brake you waste all that energy. You cannot use it in any way anymore. That's why braking hurts the fuel usage so terrible.
No. You're only looking at the kinetic energy, not the amount of fuel you burned to create it.
Fuel contains a constant amount of energy. You cannot magically create extra energy out of the fuel.
When you burn more fuel you get more energy, when you burn less you get less.
The only difference can be when the fuel isn't all burned properly. With older Diesels that creates the black smoke plumes. But with a normal modern engine that makes very little to now difference.
The simple statement about the constant amount of energy you can get from a liter fuel, holds true even when you compare a F1 engine to the engine in your own car.
Of course the F1 engine creates a lot more HP by using a lot more fuel. But when you do the calculations you will find that it got the same amount of energy from the fuel.
That is also why you use 20% more LPG in an engine compared to gasoline. The Engine works just as efficient with LPG as with gasoline, but since LPG contains 20% less energy, you need to spend 20% more of it to get the same performance from the engine.
* Cruise Control
I don't know about you guys, but I also drive smoothly without cruise control. Anybody who has earned their drivers license should already be doing that.
I save absolutely NOTHING by using cruise control !
But you do! As you won't adjust your speed (a bit) all the time, you're not accelerating. Even when you think you're keeping a constant speed, you're probably reacting to the traffic around you and increasing/decreasing your speed often.
No I DON'T !!
Remember that I tested all of this in real life in real life conditions.
No with some artificical tests like that website did.
I drive 200km to and from my work every day with the same conditions on the road every week. (traffic jams are very reliable....)
REAL Life has proven that I don't save anything. Now the only thing that remains for discussions is WHY I don't save anything.
I live in the Netherlands so if anybody should see an improvement from that tip, it should be me. [/quote]
Although small increases have a much lower fuel economy penalty than larger or faster ones.
Well, if the penalty becomes immeasurable small, it's not really a great tip for saving fuel is it?
And that is what started the thread. Great tips for saving fuel....
* Excessive idling.
Nice results in their test, but not applicable to real-life at all!
They drove 10 miles, stopping 10 times for two minutes.
Just think about that. Who has ever experienced such a situation in their life?
Most people, when driving through a city, I guess.
Lots of people would guess so. But try to verify it next time you drive through a city.
You'll be amazed and how short the waiting time for traffic lights actually is. Two minutes will seem like an eternity. But you will probably spend only 40 seconds on average.
Then there is the next problem that it is only usefull when you stop two minutes.
If you stop 30 seconds you are actually hurting fuel consumption. (starting an engine wastes a little fuel)
So when you reach that traffic light, how will you predict how long you have to wait?
That is why that tip that looks very usefull, isn't anymore when you want to apply it in real-life conditions.
Conclusion:
When I use their advice in real life I can save little to nothing!
Or you didn't do it as they said.
Well, maybe we can ask everybody here to try it out themselves and collect the results in a poll?
When I drive "normal", it's pretty agressive, and I get 7.7 km/liter. When I drive like a grandma, it becomes 11.8 km/liter. Although I did experiment, I haven't got the patience, and gas still isn't so expensive that I care. Although I don't like what I have to pay to fill my tank.
Gas prices in the Netherlands are skyhigh, so I care....
Nah.. I'm used to those prices. But I'm always interested in such tips to see how big the margin of error is between artificial tests and real life.
If the difference was worth the effort, you would expect everybody would already be using it. It's not like these things have only recently be discovered.
7.7km/liter Hmm sounds like a typical american fuel gobbling car
What kind of car do you drive actually? And where?
The only time I only got so low was when I drove 400km in Germany at 110mph... And remember that was with LPG with takes 20% more fuel...
And of course in cities. And unfortunately no amount of tips can help there.
When that traffic light turns red I can't choose to coast. I have to brake and waste a lot of energy... And even when you can coast to the traffic light, the people behind you won't like it.
