Got my road tax renewal notice today and enclosed was a leaflet from dept of transport on how to save money driving.
One tip was: 'dont coast downhill or towards the lights in neutral as this uses more fuel! Stay in gear and ease off the gas gently to reduce fuel flow to the engine to virtually zero.'
I read somewhere new engines are designed not to use fuel on the overun (decelerating using the engine) would this apply to a 2002 Toyota Corolla ?
It would apply to pretty much anything with fuel injection and an ECU, so yes. The saving would be pretty trivial though.
As always however, the best way to save fuel is to not use the car! Walk if possible on short journeys, and try to plan trips so you can carry out a number of tasks in one journey.
Actually it more complicated than it seems. Nearly all fuel injected cars will have an overrun fuel cut off which means that they use no fuel on the overrun as opposed to a trickle of fuel when coasting.
That said, with no fuel being burnt, there will be increased drag so your car will decelerate faster. On a gentle hill that you might be able to coast down, if you leave it in gear you will actually have to use a certain amount of throttle to maintain the speed that you could have achieved freewheeling.
Depending on the length and duration of freewheeling, you could use less fuel with the engine idling than the fuel required to maintain road speed on a gentle downwards incline.
I know that by judicious use of freewheeling I was able to improve the economy of my diesel Touran but it had a DSG gearbox which made it very easy and smooth to slip between drive and neutral.
As Mr Cheerful has pointed out though, it is actually against the law.
The overrun fuel cut on petrol engines is triggered by the throttle being shut so the idle switch is on with the engine rpm higher than the idle soft landing rpm. Some may also detect gear from speed and rpm inputs. The soft landing rpm is usually around 1500rpm. RPM lower than that will switch fueling on so it doesn't stall when/if rpm drops to idle.
Select a gear that keeps rpm up around 2000. A gear that runs engine faster will be excessive drag - engine braking rather than easing off and not fuel efficient.
If you are lame about lifting off and obey the GOV instruction "ease off the gas gently", then fuel will still be supplied as the idle switch isn't ON until foot is fully off the throttle.
Diesels can't call it a throttle pedal as Diesels don't have throttles. Governor pedal? Demand pedal? Oil pedal? Smoke pedal?
When I was having driving practice in my uncle's 1936 Morris 10/4 it had a freewheel, and coasted whenever you lifted off the gas/accelerator/loud pedal...
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