driving to save fuel... a myth or truth?

[mstar]

one thing my old man, keeps saying is that to save fuel when cruising down a hill, or traffic lights which are approaching red - place the car in neutral and using the momentum cruise, and dnt use the accelartor, and when ur going tooo slow put in approriate gear and speed up again, and drive

Having said that my next door neighbour said that u should be aiming to reduce gear changes and fuel consumption is related to accelrator usage (i.e pressing it) not gears.

does anybody know the best way in the 2 ways described, its baffling me? also any difference in fuel type/model/year of car? i guess its a question does fuel still get fed in the engine when in gear or neutral, and then when getting to slow put in approriate gear matching speed ur at.

 

[television]

Your car should be kept in drive the whole time, we have earlier had this debate and with an auto you leave it in drive, as nothing is gained by using N

Re the fuel, you are wasting your money putting in a higher octane rating than the engine needs, you do not say what car you have, to get the best economy, its a matter of thinking ahead,avoid rapid speed changes, get into top as soon as possible, if the lights are Red 100 yards down the road, your foot should be off the throtle, A heavy right foot, does cost money.

Malcolm

 

[anyweb]

my mum once tried to save on fuel one day many years ago in Ireland, at that time we were pretty poor and our family car was an old FIAT 124 (basically what the LADA is today), anyways, she went one step further on this notoriously bendy downhill road (you may know of it, it's called the 'curlews' in Boyle) and turned off the ignition while setting the car in neutral. Sure enough when the next bend came, the cars steering and drive didnt help and we ended up in the ditch (5 kids in the car). None of us were injured and some helful motorists helped man-handle the car out of the ditch.

Thankfully, as the old FIAT was a piece of junk to begin with, the dents on it were hardly noticeable against all the other dents it had (we got it second hand) and as it was such a banger, we didn't care at all !

just wanted to let you all know !

cheers
anyweb

 

[Rory]

does fuel still get fed in the engine when in gear or neutral,

This is the key point - coasting in neutral uses fuel (to keep the engine idling).
Running downhill in gear (or drive in an auto) 'on the overrun' causes fuel in all modern cars to be stopped, so the car isn't using any fuel at all.

Coasting causes all sorts of dangers that may not be immediately apparent - the car isn't really under control, and some cars have engine speed dependant power steering, which gets very confused by an idling engine and the car doing 70MPH.

The big thing that uses fuel is speeding up to regain your desired speed - ideally you should try to predict traffic flows etc, so that you can minimise having to slow down and then having to speed up again. Stop/Start in Mercs seems tokill the fuel consumption, so trying to predict lights / roundabouts etc is useful.

 

[mstar]

you do not say what car you have,

Malcolm

sorry guys 1998 C250 TD (manual), i forgot to mention

 

[SLinKyjoe]

keeping the foot off the throttle down hill will not use fuel. everything else will. the harder you press the more you use but as you have a manual you will be able to select a higher gear for decending downhill and maybes keep a more even speed for the level bits.

in mine, which is an auto, on the motorway i put in M so it doesnt change down when i press the accelerator to pass things, which makes it drive more like a manual. Bear in mind that as mine is an AMG it is very sensitve to throttle pressure and drops gear at the slighest pressure. By doing what i do makes a noticable difference.

You could try a few economy runs and see what difference both styles make.

I got 42mpg (over 132miles) out of a subaru WRX by driving at a consistant speed and using only gentle throttle. And by hooning it i could easily drop it to 19mpg.

 

[Badshot1uk]

Ive heard that using cruise control is a great way to save fuel as you remain at a constant speed (traffic permitting).

Not sure if its true or not, but I tend to use it.

It definatly helps to try and predict traffic flow and act accordingly to avoid hard breaking and acceleration too.

Paul

 

[tom7035]

Any use of the brakes whatsoever means fuel wasted so it's as has been said - advanced observation/prediction to hone up your acceleration/deceleration sense.
Provided the car is all in order it doesn't waste fuel, its driver does.

 

[roundlet]

How can you drive to save fuel?

 

[television]

How can you drive to save fuel?

Think yourself lucky that you were not around driving in the 60's, there were many devices for saving fuel, in fact there were so many claims of saving up to 20% if you added them all together you could have sold the spare petrol.


Malcolm

 

[mike65]

Smooth driving saves fuel as does making sure you a don't have a storage box on the roof, dont have the sunroof open/windows down, have under-inflated tyres, boxes of crap in the boot, several kilos of mud inside the wheel arches. Learn to anticipate traffic lights, if they are on green in the distance ease off cos they'll be red by the time you get there!

Mike.

 

[tom7035]

Think yourself lucky that you were not around driving in the 60's, there were many devices for saving fuel, in fact there were so many claims of saving up to 20% if you added them all together you could have sold the spare petrol.


Malcolm

Not too long ago on this very forum some members were gullible enough to buy magnets to clamp onto the fuel pipe!! (To 'straighten out the ions' or some such cr-p and even recommended them to all and sundry!)

 

[Bobthebuilder58]

Saving Fuel!

:smile: :smile: My best tried and tested fuel saving tip is to...........borrow the wifes car
I am currently getting 26mpg out of my 500 SEL by driving very carefully.

Bob. ......hoping my good lady doesn't see this post

 

[television]

Not too long ago on this very forum some members were gullible enough to buy magnets to clamp onto the fuel pipe!! (To 'straighten out the ions' or some such cr-p and even recommended them to all and sundry!)

Thanks again Tom, it sounds like the special drawn HI FI loudspeaker cable at £100 per meter, I always said that the best sound was when you opened the till to put the money in, and the little bell went "ping"

Malcolm

 

[johnmc]

Hi,
I just got back from yet another long haul drive to Italy, 1,500miles, and have to say that I noticed difference in the cost of fuel this year. It's about 85p/litre now on the continent for diesel. I tried various ways to reduce my cost on the run, but the bottom line is that these are the two biggest factors:
1. The driver's foot, slow down and don't floor it. In my car driving at 70mph instead of 85mph gains 7-10mpg. Things like minimal braking, not racing up to traffic jams or lights (keep the car moving) definitely work. Coasting can help a little, for example if you're going down a hill and engine braking is slowing the car too quickly, it can keep you moving without throttle input for longer.
In a long drive the difference it makes is small, and I couldn't recommend it, especially as going down a hill is where you really want the engine braking..!

2. The terrain. Going up a hill needs more fuel, nothing you can do about it. My mpg climbing through the alps crashed down by 10mpg.

The other stuff like reducing load, turning off the aircon etc do help, but the impact is so tiny compared to your own lead foot you'll be pushed to see anything unless you are driving with feathers on the throttle..!

I notice in the USA that sales of 4x4 are down 50%, and saloons/estates are increasing fast.

Cheers!
John

 

[tom7035]

Many moons ago, one of the tests in the Scottish Police Advanced Driving Certificate course was making a journey between Edinburgh and Glasgow on the A8 (before the days of the motorway) which for a large part was UNDIVIDED three-lane carriageway, in a 3.4 Mk 2 'S' type Jaguar without touching the brakes for the entire journey! This was checked by dusting the brake pedal with talcum powder at the start of the journey. What made it all the more incredible was that MAXIMUM PROGRESS had to be made while at the same time obeying speed limits rigorously, apart from the National speed limit where there was special dispensation for Police training cars.
Believe me, with training it COULD be done and was, regularly.
(And I know this story to be true, because I was one of those who did it).

 

[Wezzel]

I stopped using cruise control because I found it used more fuel. Running without it I tend to very slightly speed up on the downhill bits and use the momentum to help on the inclines (therefore losing a little speed before increasing the right foot too much). This actually works out more economical for me.

 

[DuncanClarke]

I have often wondered wether turning on the A/C and keeping the windows closed will actually save fuel, due the the extra drag caused by an open window

Duncan

 

[jp williams]

How can you drive to save fuel?

I have an E class auto estate e220cdi done 59,000 and regularly get between 45/55mpg.Use cruise when you can and do not exceed75/80mph.Anticipate a need to slow down and use brakes as little as possible,then accelerate away gently without pressing the accelerator to the floor.
Happy driving!

 

[3146bj]

I have often wondered wether turning on the A/C and keeping the windows closed will actually save fuel, due the the extra drag caused by an open window

Duncan

Ford Australia did some work a few years ago on how the a/c affected fuel consumption. They found that at 100km/hr one open window (with a/c off) increased the drag and fuel consumption about double the increase caused by having the a/c on and windows closed. From memory, an open window used about an extra 2l/100km at a constant 100km/hr. I think the car was a 1994 or 5 Falcon sedan which doesn't have the most effeicient aerodynamics.

An aside on fuel consumption a friend once achieved 84 mpg with a 1967
Renault 8 on a car club economy run (any other oldies remember the Mobil Economy runs of the '50's and '60's?). He ran very high tyre pressures and used very light throttle, accelerating very gently and, where possible, down hill. A very high level of concentration is needed to anticipate traffic flow and minimise the need to brake. It did, however, remove any chance of enjoying a drive.