Would you like to save up to 30% of your current fuel costs by just changing the way you drive?
Not everyone can afford to upgrade to the latest eco-friendly car models, so in this
video we will show how we can use 10 eco-driving tips to make a real difference to our fuel
economy.
We will be driving a short route twice, and the only thing we will change will be the
way we drive the car. We will reset the car’s average fuel economy indicator each time,
and although it won’t give a 100% accurate result it will be good enough for comparison
purposes. At the end of the video we will use the results to estimate the savings over
a whole year of driving - which should be interesting!
On this first drive we will be using eco-driving techniques, to maximise the car’s fuel economy.
The car’s engine is already warmed up and we we will be driving a short route on a mixture
of roads. Let’s set off…
At first the average fuel economy readout on the dashboard doesn’t show a reading,
but keep an eye on it as we drive as it will keep updating itself.
We usually try to accelerate the car gently, as harsh acceleration is the main cause of
poor fuel economy. The harder we press the accelerator down, the more fuel will be injected
into the engine - so we press the accelerator gently and smoothly to only use as much fuel
as needed. Of course, sometimes we will need to accelerate the car quickly, such as when
we're joining a dual carriageway so we would use as much throttle as we need to keep up
with the flow of traffic and then return to gentle use of the accelerator.
Keeping the engine running at it’s most efficient speed is key to saving fuel, so
we should change gear whenever necessary. In a diesel car like this we would normally
keep the engine below 2000rpm, but if we had a petrol engine we would use up to 3000rpm.
Most modern cars have a gear-change prompt on the dashboard so we can use this for guidance
if needed - on this car we can see it appear under the outside temperature display. When
we need more power we will sometimes need to use more engine revs, but once up to cruising
speed we would change to the most efficient gear again.
We use the ‘Lift & Roll’ technique to use the car’s momentum to travel for free!
Lifting fully off the accelerator for a few seconds before braking for a corner or junction
will save loads of fuel, as the car uses no fuel at all when rolling in gear. This technique
is part of the skill known as ‘acceleration sense’ and when combined with good forward
planning can give considerable savings - we can see the average fuel economy reading increase
as we 'lift & roll' on approach to each junction. In contrast, lifting off the accelerator pedal
and braking immediately wastes the momentum that we had just used fuel to gain.
We can see on the map that we are about 1/3 of the way around our drive, and the fuel
economy is just under 70mpg so far!
Braking earlier will not only give a smoother ride to our passengers, but it will also save
fuel! When we brake, we are turning the momentum our car has into heat within the braking system.
Lifting off the accelerator earlier, and braking earlier and more lightly will minimise the
amount of fuel we are turning into heat - and also extend the life of the car's braking
system.
We should use our observation skills to read the road ahead, so that we spot bends or hazards
ahead as early as possible. This will then allow us to 'lift and roll' more often, which
will save more fuel than if we just braked to reduce our speed. This early speed reduction
will also give us more time to assess the situation so there is less chance of making
a mistake that might put us in danger.
Exceeding the speed limit on major roads is very poor for fuel economy, as our car’s
wind resistance increases sharply at high speeds. Since air resistance is such a large
factor in how much fuel a car uses, the most efficient speed is around 40mph for most cars.
However, we should ensure that we only drive at this speed where appropriate and keep up
with the flow of traffic, as driving unnecessarily slowly will annoy other drivers and cause
danger.
We are now about 2/3 of the way around our drive, and the fuel economy average is still
just under 70mpg. The faster roads we’ve just driven did use a little more fuel, but
the last section of the route is slower so we might get a little increase before we stop.
Don’t take the car out of gear and coast in neutral, or coast with the clutch pedal
pushed down as this actually wastes fuel. When rolling in neutral, the car’s fuel
injection uses a little fuel in order to keep the engine idling, but when the car is rolling
in gear the car’s momentum is turning the engine without using any fuel at all. Coasting
out of gear or with the clutch pressed down will also give us less control over the car's
speed so is not recommended on safety grounds.
We try not to idle the engine unnecessarily - and switch it off when pulled over at the
side of the road or when stuck in traffic. Many modern cars have 'start stop' systems
that do this automatically, as this feature can save up to 10% of our fuel on it’s own.
We wouldn't bother turning the engine off if we are only stopping for a few seconds,
but we would if we think we might be stopped for 30 seconds or more.
When driving in traffic we look out for other vehicle’s signals such as an indicator or
brake light that show they are about to slow down. When we spot this we can then lift off
the accelerator or brake to reduce our speed and create a little extra space that will
allow us to keep rolling whenever possible.
Using the car’s air conditioning system does use some power from the engine, so this
will reduce fuel economy. This is more noticeable when driving at low speed, so unless the air
conditioning is really needed we would switch it off and open a window instead. At higher
speeds the extra aerodynamic drag from open windows will increase fuel consumption so
it’s better to keep them closed and use the a/c if its needed.
So thats the end of this first drive, and the average fuel economy we achieved with
eco-driving was 69.8mpg. Let’s reset the fuel economy meter, and drive the same route
again without using any eco-driving techniques. How much difference do you think it will make?
As we set off this time we will be driving normally, but without any consideration for
saving fuel. We will still be driving safely, and within all speed limits - but we will
be accelerating up to speed more quickly, and braking much later than before. We will
also be using more engine revs in each gear, and staying in lower gears more of the time.
While we drive, keep an eye on the economy readout and see how it compares to the previous
drive.
So you have probably worked out by now that eco driving is all about preserving momentum.
We use our engine carefully to gain momentum with as little fuel as possible, and then
we plan ahead so that we use this momentum to take us as far as possible. Whenever we
use the car’s brakes, that will turn our momentum back into heat - which is then wasted,
so for maximum efficiency we try to reduce the amount of time we spend braking the car.
While we drive the second route, we have 5 extra tips we can use to help our car give
its best fuel economy possible:
First of all we always try to keep our cars well maintained. Regular servicing helps the
car stay reliable and efficient, as it will keep the engine in tune which reduces emissions
and improves power and fuel economy. In addition the garage will check the steering and braking
systems which is essential for safety.
A correctly inflated tyre has less rolling resistance than a under-inflated tyre - so
we check our tyre pressures regularly to optimise our fuel economy. Also, when a tyre is under-inflated
it will wear out much faster, so we keep an eye on pressures to get the best life from
our tyres.
Driving around with unnecessary weight in the car will make the engine work harder,
and as a result use more fuel. If we don’t need it, take it out.
Roof boxes and roof racks are useful, but they create a lot of extra aerodynamic drag,
which will make the car’s engine work harder - using more fuel. So we remove everything
from the car’s roof once it's not needed any more.
If possible, we try to plan our journey in advance so we avoid busy traffic. The constant
stopping and starting wastes fuel and is much more stressful for the driver. If we allow
plenty of time and drive when the roads are quieter it is much more enjoyable and efficient.
So, that’s about 1/3 of the route and we can see our average fuel economy is just above
40mpg, which is far lower than last time when it was almost 70mpg. We’ll fast forward
the video for a little bit…
At 2/3 of the route the economy has improved a little to 45mpg, but it is still far below
last time, when we achieved just under 70mpg at this point. Let’s fast forward to the
end to get the final result.
So that’s the end of the second drive, and we can see that in the exact same car and
conditions we achieved 45.8mpg this time. We completed the route 30 seconds faster than
the first time, but used 52% more fuel.
We can now estimate how much money we could save over a whole years driving: If we drove
10,000 miles at an average fuel economy of 45.8mpg and fuel price of 120p per litre it
would cost us £1191. That’s reasonably efficient, but if we could improve our fuel
economy to 69.8mpg it would only cost us £782. So in this case eco driving could save us
£409, or about 34% - very impressive!
So, remember to: Accelerate gently
Keep the engine speed low ‘lift & roll’ wherever possible
Brake early and lightly
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