Saving petrol

johnniekewl

Some general questions about conserving petrol when driving.
Q1:Do you save much more petrol by driving in 4th gear and keeping your RPM lower than if u were in 3rd gear?
Q2:When stopped in traffic if u turn ur engine off will it save u much petrol?
If u do turn off the engine will the repeated turning on and off of the engine effect it's performance?
Q3: How much petrol does free wheeling save?
Any tips on how to conserve petrol while driving?

Big Nelly

johnniekewl wrote:

Some general questions about conserving petrol when driving.
Q1:Do you save much more petrol by driving in 4th gear and keeping your RPM lower than if u were in 3rd gear?
Q2:When stopped in traffic if u turn ur engine off will it save u much petrol?
If u do turn off the engine will the repeated turning on and off of the engine effect it's performance?
Q3: How much petrol does free wheeling save?
Any tips on how to conserve petrol while driving?

Simple answer to all of these........BUY A DIESEL!!

seamus

johnniekewl wrote:

Q1:Do you save much more petrol by driving in 4th gear and keeping your RPM lower than if u were in 3rd gear?

Yes and no. So long as the engine isn't struggling, then driving at lower RPMs should help conserve petrol. For my car (Peug 206) the optimal is between 2k and 3k revs. Much below this and the engine will struggle.

Q2:When stopped in traffic if u turn ur engine off will it save u much petrol?

There was a discussion on this before if you search. IIRC, the general consensus was that if the traffic was heavy, and you were completely stopped for a few minutes at a time, then yes, it can conserve petrol. But if you're constantly moving, or only stopping for 30 seconds or so at a time, then you'll actually burn more fuel by turning off the engine.

If u do turn off the engine will the repeated turning on and off of the engine effect it's performance?

It can. If the engine is cold and you repeatedly turn it on and off you can end up doing long-term damage.

Q3: How much petrol does free wheeling save?

Not enough to make it worthwhile.

Guy:Incognito

johnniekewl wrote:

Some general questions about conserving petrol when driving.
Q1:Do you save much more petrol by driving in 4th gear and keeping your RPM lower than if u were in 3rd gear?
Q2:When stopped in traffic if u turn ur engine off will it save u much petrol?
If u do turn off the engine will the repeated turning on and off of the engine effect it's performance?
Q3: How much petrol does free wheeling save?
Any tips on how to conserve petrol while driving?

Cycling is the answer to your questions.

bazz26

johnniekewl wrote:

Some general questions about conserving petrol when driving.
Q1:Do you save much more petrol by driving in 4th gear and keeping your RPM lower than if u were in 3rd gear?
Q2:When stopped in traffic if u turn ur engine off will it save u much petrol?
If u do turn off the engine will the repeated turning on and off of the engine effect it's performance?
Q3: How much petrol does free wheeling save?
Any tips on how to conserve petrol while driving?

None of these will make much difference to your mpg, at least not enough difference for you to notice it.

If this little saving on petrol is really crucial to you maybe it is time to look at changing to a more economical car altogether, maybe a supermini or city car.

damo605

johnniekewl wrote:

Q3: How much petrol does free wheeling save?

None apparently! If you are free wheeling the engine uses a small amount of petrol to idle and stop itself from stalling but if you leave the car in gear while slowing down the engine should use no petrol at all.
Heard that on Top Gear!

Push bike is the right job for ya

commited

What car do you have?
Basically, neglecting wind resistance and drag, you will get max fuel economy at peak torque. In most petrol cars this is around 2500rpm - find the figure for your car though.
Other than that gentle acceleration and anticipating what's going to happen ahead (so that you dont speed up to slow down again) helps too.

maidhc

The best way to save petrol/diesel is not to floor it when accelerating and use a sensible gear. There is rarely an occasion where it is necessary to redline a car from the traffic lights, and it is really silly to do 50-60 in 4th gear or 15mph in 1st.

I would say that you would save a considerable amount of petrol driving in 4th than 3rd, provided your cars isnt labouring and in a state of stalling. My mondeo 1.8TD (Diesel) will cruise happily at 30mph in 4th, and it isnt considered the most lively of cars.

johnniekewl

i'm driving a subaru legacy,2.o litre-All Wheel Drive.

stevenmu

Basically the car will use the same amount of fuel at say 2.5k rpm in 4th gear as it will at 2.5k rpm in 3rd gear, or even 2.5k in neutral (ignoring wind resistance etc). It's each revolution that uses fuel, not the distance you travel, and because you travel further per revolution in higher gears you use less fuel to make your journey.

Supercell

hmm i wonder how much of this post is pure conjecture.
I remember getting taxi rides on Greek islands on holidays and the taxi drives always coast where ever possible, and on big hills turned off the engine totally..was very weird to experience.

I really doubt they do this for the craic and there is some nwt benefit in petrol used.
That said in the med the hills are on average much much steeper than the ones we have here so perhaps the same dynamics dont apply.

commited

Longfield wrote:

hmm i wonder how much of this post is pure conjecture.
I rember getting taxi rides on Greek islands on holidays and the taxi drives always coast whereever psssible, and on big hills turned off the engine totally..was very weird to experience.

I really doubt they do this for the craic and there is some nwt benefit in petrol used.
That said in the med the hills are on average much much steeper than the ones we have here so perhaps the same dynamics dont apply.

Older cars are different - its newer cars that use little fuel coming to a stop. You shouldnt coast anyway, it's bad driving practice.

From what I can see - 3600rpm is where your peak torque is which is pretty high

fletch

Longfield wrote:

hmm i wonder how much of this post is pure conjecture.
I remember getting taxi rides on Greek islands on holidays and the taxi drives always coast where ever possible, and on big hills turned off the engine totally..was very weird to experience.

That's a VERRY dangerous thing to do.....your brakes will be next to useless, ur steerin will be really heavy, ur airbags prob wouldn't deploy in an accident etc etc...

SouperComputer

this is what I do anyway, I found on overage im getting 30-40 miles a tank extra. Most cars I have done it with liked it, both big and small. Although a VTEC Civic Del Sol really needs a bit more revs than mentioned below.

1. Use as little throttle as possible, a good rule of thumb is to pick a throttle position that the engine will not rev beyond 3000 in a given gear.

2. Go up though the gears as quick as you can, bearing step 1 in mind and also you dont want to labour the engine. If you dont require much acceleration than you can keep the revs as low as 1500RPM without labouring, sometimes even less. So if you are not in traffic, you might rev up to 2500 for 1st and 2nd and maybe 1800 for third, then 1500 and streight into 5th

3. As cormie said, leave a good gap in front of you and imagine trying to keep you acceleration & decelleratins to a minimum, use as little brake and as little throttle as needed.

4. Freewheeling can work if the revs are kept above idling. If you put an injection car in neutral, it will set the throttle up for idling if the revs drop below idle speed. So when on the overrun, @1500RPM and above, the ECU should realise that fuel is not needed.

5. We all have junctions that we are used to and know full well we are going to be stuck there for 2,3,4 or even 5 mins. In those cases its beneficial to stop the engine.

6. If you have cruise control, use it!


Thats all I can think of. Again, how well it works depends on the gearing and power curve of your car.

mike65

my car (Peug 206) the optimal is between 2k and 3k revs. Much below this and the engine will struggle.

That must be pain in the ass, sounds like you spend most of your life in 3rd gear seamus.

Another thread on this topic

Mike.

Victor

Longfield wrote:

hmm i wonder how much of this post is pure conjecture.
I remember getting taxi rides on Greek islands on holidays and the taxi drives always coast where ever possible, and on big hills turned off the engine totally..was very weird to experience.

I'm guessing he was trying not to overload the airconditioning.