I’m a fan of getting that extra mile out of a tank of petrol (well diesel… but ya know), and as such have been known to allow my car to freewheel up to lights… I mean come on… surely freewheeling (despite the illegalness) has to be the most efficient… right?
Well it turns out… NO…
If you take the car out of gear, the engine needs a little fuel so it doesn’t conk out. If you leave it in fuel the idea is that the engine is kept going by the inertia, and so doesn’t need fuel.
So its like this, if you are going to free wheel for a very long way… then it will make sense. If it’s a shorter distance like up to the lights, then leave the car in gear. The engine will actually take energy out of the wheels to keep going, and so use less fuel. It will also slow the car a bit, and so you’ll need less breaks… do the savings ever end?
greennav
martinfaulkner
micallc
thenewoil
ciablasar
April 29, 2008 at 5:23 pm |
I have submitted your article to http://www.autocar-live.com which is a social site about cars where users submit car/auto articles they like and vote for articles that others submitted and they like.
May 1, 2008 at 7:50 pm |
In the UK in the 1970s my father drove a standard transmission Saab 95 which had a freewheel like a bike. It coasted under momentum unless the accelerator was applied. Under the dashboard was a lever you could pull (when the car was stationary) to put the car into the more familiar “fixed wheel” mode, which was recommended on steep and twisty roads.
This brilliant but simple idea made the car very economical to run. The only modification to driving behaviour was slightly more reliance on braking rather than the engine to slow down – an adaptation that anybody who had ever ridden a bicycle could make in minutes.
At some point freewheel mode became illegal in the UK, on alleged safety grounds. Yet in our experience the car was safe to drive almost everywhere. It was only on mountain roads with hairpin bends that my father ever felt the need for “fixed wheel”.
I have never believed the line that freewheel mode was inherently unsafe, and believe that the time is right to reappraise the idea. The environmental and economic benefits may well outweigh a small difference in safety, if it exists. If an optional freewheel mode were made standard in new cars worldwide the savings in greenhouse gases could be absolutely enormous.
**Please forward this letter and let’s get optional bike-style freewheels in cars onto the political agenda.** Now that governments are finally dumping incandescent bulbs and banning plastic bags the time is right.
George Lee Vancouver, Canada
June 27, 2008 at 9:32 pm |
I am a believer in freewheeling. I drive a Toyota Sienna, and even with the third row of seats taken out it is still quite a weight. As there are a number of hills round where I live, I freewheel and it’s both safe (as long as the road is reasonably straight) and I believe – am I right? – that it saves me gas. The weight of the Sienna certainly takes me faster more quickly, unless I was pretty hard on the accelerator.
June 28, 2008 at 8:02 pm |
Hi Charles,
I think it realy depends on the length of the freewheel. If your free wheeling for a long distance then there may be merit, but my research found that when you freewheel up to lights, and so breaking, it would have been better to let the engine slow the car, as it can use the momentum to keep the engine going, instead of petrol
thanks for the comment
P