As a serious point' date=' though, diesel engines use virtually no fuel at idle, but a relatively large amount when starting up. This is why truck drivers often leave their engines running when they park - same as how if you're going out of a room with fluorescent lighting for less than 15 minutes, it actually consumes less electricity leaving them on...[/quote']

Not sure thats true... my MPG used to plumment when I was stuck in traffic going to and from work and it would never regain normal levels.

Not sure thats true... my MPG used to plumment when I was stuck in traffic going to and from work and it would never regain normal levels.

I've noticed the same ...

Steve

Chris I would check because with most cars with power steering if the engine stalled you would loose the ability to steer easily and also brakes would be alot harder to use as well as the engine aids the master cylinder does it not ? :rubchin:

When I say coasting, I just mean driving with the clutch down (the car is in the same gear it was in when you were driving) so in theory the car shouldn't stall as there is no load on the engine..........

As I said, I'm not condoning it or saying I practice it, just saying that letting the car run at idle while you're moving will save you fuel

Chris

Not sure thats true... my MPG used to plumment when I was stuck in traffic going to and from work and it would never regain normal levels.

The reason why I suspect your MPG suffered is that relative to the distance you've travelled, you've used a lot of fuel. For example, if you're sat on the motorway in 6th with the engine ticking over just above idle, you'll be doing 60 miles every hour. If you're sat in a traffic queue, even though you're using a similarly small amount of fuel you may only travel 5 or 6 miles in the same hour..... Plus in traffic queues, there's a lot of start/stop which will increase the amount of fuel used too....

Chris

The reason why I suspect your MPG suffered is that relative to the distance you've travelled' date=' you've used a lot of fuel. For example, if you're sat on the motorway in 6th with the engine ticking over just above idle, you'll be doing 60 miles every hour. If you're sat in a traffic queue, even though you're using a similarly small amount of fuel you may only travel 5 or 6 miles in the same hour..... Plus in traffic queues, there's a lot of start/stop which will increase the amount of fuel used too....

Chris[/quote']

That's exactly my point - I wasn't talking about being stuck in traffic, I was talking about being parked for short periods. Like Chris says, it's the stop-start nature of driving in traffice that kills your MPG...

As I said' date=' I'm not condoning it or saying I practice it, just saying that letting the car run at idle while you're moving will save you fuel

[/quote']

Leaving it in gear, with no throttle whilst moving will save you even more! You can hear this (with the window open) as the engine goes quiet - no fuel being injected and therefore burnt. You can also see this on the MPG readout as it will say --- mpg.

When I say coasting' date=' I just mean driving with the clutch down (the car is in the same gear it was in when you were driving) [b']so in theory the car shouldn't stall as there is no load on the engine..........[/b]

As I said, I'm not condoning it or saying I practice it, just saying that letting the car run at idle while you're moving will save you fuel

Chris

OK try this, start the engine and when it's idiling turn the steering wheel, you will notice the engine note dropping so there is load on the engine as is the same when you apply the brakes, so it is possible to stall the engine.

Hi to All

In these days of ludicrous speed limit enforcement and traffic clogged roads, sometimes, the only kind of entertainmet left is to see how much fuel you can save. Having played this game a few times, I have found the following to help (reasons I think it helps in brackets):

Anticipate everything by using good observation and planning this will reduce the number of times you brake and accelerate. (Braking is throwing energy out of the system as heat, acceleration is repalcing that energy and uses fuel)

Plan your journey to avoid traffic jams, routes with steep gradients and excessive miles if possible. (Obvious really)

Use overrun in high gears when going down gradients. Coasting for prolonged periods must lead to acceletated wear on the clutch bearings unless you knock it into neutral. Both are dangeraous as they reduce the control you have over the car and reduce the effectiveness of the brake servo. (Coasting requires the engine to use fuel to maintain idle, overrun condition does not).

Use perhaps half or a little more throttle and 1700 to 2100 rpm, or around peak torque for whatever you drive, for accelerating. (Under using the throttle is in theory using less fuel, however, the engines volumetric and thermal efficiciencys are much reduced at very small throttle openings or very low revs, so you run less efficiently for longer. Over using the throttle and paticularly the revs increases frictional losses ).

Ensure your tyre pressures are correct and avoid wider than standard tyre fitment. (Wider tyres mean more tyre deformation to for a contact patch leading to increased rolling resistance. Underinfaltion is both dangerous and uneconomical due to increased rolling resitance and increased heating of the tyre carcass).

Avoid short hop journeys, walk down the corner shop!

Doing all of the above religeously may well save you

Leaving it in gear, with no throttle whilst moving will save you even more! You can hear this (with the window open) as the engine goes quiet - no fuel being injected and therefore burnt. You can also see this on the MPG readout as it will say --- mpg.

So if you're sitting at 2k rpm, and you lift your foot off the accelerator but are going downhill so you're maintaining 2k rpm, how can it not be injecting fuel, as the engine requires fuel to turn over? Or am I missing something fundamental here? ... wouldn't be the first time

Chris

So if you're sitting at 2k rpm' date=' and you lift your foot off the accelerator but are going downhill so you're maintaining 2k rpm, how can it not be injecting fuel, as the engine requires fuel to turn over? Or am I missing something fundamental here? ... wouldn't be the first time

Chris[/quote']

Chris I can see his point, think of it this way, if you need to maintain 1000rpm you will require fuel, if you are dragging the engine ingear at 2000rpm and you take your foot of it you are essentially telling the engine to maintain tickover but as you are already doing 2000rpm you won't have to inject any fuel into the cylinder to get it to that magical figure. Just a theory

So if you're sitting at 2k rpm' date=' and you lift your foot off the accelerator but are going downhill so you're maintaining 2k rpm, how can it not be injecting fuel, as the engine requires fuel to turn over? Or am I missing something fundamental here? ... wouldn't be the first time

Chris[/quote']

The momentum of the car turns the wheels, which turn the propshafts, the gearbox, the crankshaft and back up to the pistons. Therefore the transmission's effective operating in reverse - i.e. the kinetic energy of the car is transmitted to the engine, rather than the energy from internal combustion in the cylinders being transferred to the wheels.

Therefore, as long as the engine revs are high enough to overcome internal friction (stalling), you are able to keep rolling along without using any fuel. Hence --- MPG as pointed out earlier.

This is opposed to the 199 MPG I once saw going downhill on the motorway, as although gravity and momentum were doing most of the work, I still needed a certain amount of throttle otherwise I'd gradually have ground to a halt. This is because travelling at any given speed is a balancing act between the work of the engine plus any gravity and wind assistance versus rolling resistance, transmission losses, drag and/or gravity resistance.

QED

however you drive you still get a dam good mpg figure!

keep the gears high but don't chug along keep 1k-2.5k and cruise control is excellent for economy i do a good run to work on a good A road, with cruise on @ 60mph in 6th it does mid 50's mpg

I'm sooo impressed with my PD100 combi's fuel figures after driving a tuned smart around for 5 yrs ...

I've just arrived back from a few days down in pasty country and the journey back (according to the dash readout) was as follows;

240 miles, 3hrs 30mins, average speed 70mph, average fuel 57mpg.

That's the length of the M5 and the A30 at warp 9, plus miles and miles of winding country lanes at 30mph.

Not bad eh?

But were is the fun, the main reason I got the VRS was because you can have a little fun and get ok fuel consumption

But were is the fun, the main reason I got the VRS was because you can have a little fun and get ok fuel consumption

Agree with you here, Just with the impending blockades and large fuel bills I want to save my fuel so I dont end up with none like last time. Trust me as soon as this fuel debacle is over I will be back to "driving like I stole it" to use another members favourite saying:thumbup:

The momentum of the car turns the wheels' date=' which turn the propshafts, the gearbox, the crankshaft and back up to the pistons. Therefore the transmission's effective operating in reverse - i.e. the kinetic energy of the car is transmitted to the engine, rather than the energy from internal combustion in the cylinders being transferred to the wheels.

Therefore, as long as the engine revs are high enough to overcome internal friction (stalling), you are able to keep rolling along without using any fuel. Hence --- MPG as pointed out earlier.

This is opposed to the 199 MPG I once saw going downhill on the motorway, as although gravity and momentum were doing most of the work, I still needed a certain amount of throttle otherwise I'd gradually have ground to a halt. This is because travelling at any given speed is a balancing act between the work of the engine plus any gravity and wind assistance versus rolling resistance, transmission losses, drag and/or gravity resistance.

QED [/quote']

Very true, and a good way to save your brakes driving downhill, I descend along the Snake Pass in 3rd, stay locked at 40ish, mega MPG and only press the brake pedal 3 times. Everyone else has their brake lights on for almost the whole 2,5 mile descent. Not good.

theres a whole article in one of the magazines this month on driving economically, I think it was what car or autocar

If you average more than 50+ per gallon whats the problem?

Best way to save money..........Give up your car...Fags...Beer.....and become a Monk.

Or live a life and enjoy it .

Steve

If you average more than 50+ per gallon whats the problem?

Best way to save money..........Give up your car...Fags...Beer.....and become a Monk.

Or live a life and enjoy it .

Steve

Guys,

I am doing my best to lower consumption when I drive but I would love to know how you work out EXACTLY the MPG you are getting. I was told to fill the tank to a known level with a known amount and then work out the miles covered with the reset trip mileometer. I worked out about 38 MPG for my 105 but I would love to find out more exactly.

My colleague said you can work it out with GPS but did not know the method.

How do you work out your MPG?

Cheers in advance,

Ian

Fill up to the brim at a garage , drive for as long as you want , then fill up to exactly the same point on the tank. You really need to fill to the brim as otherwise you will always end up with slightly different amounts of fuel in the car.

You then know the distance you have travelled and the amount of fuel you have used and can sit down with a calculator.

Thanks for that!

Will try when I fill up today.

Cheers,

Ian

The thing I've found has helped most - seems to have gained me 5mpg or so in a PD100 Fabia estate - is just keeping the acceleration down - short of that kick-in-the-back boost. I've also trimmed my top speed from about 80 to 75 (only on private roads, of course) and I can now get 55mpg without dawdling on a mixed A/B/M roads trip of 40 miles or so, even with the heavy traffic at the start and end.

As for calculating exact MPG figures, I just reset the trip counter every time I fill up and compare with the number of litres I've bought - which is listed on the receipt. That way it doesn't matter how much or little you put in each time, because you have what I would think is a reasonably accurate figure each time.

Fill up to the brim at a garage , drive for as long as you want , then fill up to exactly the same point on the tank. You really need to fill to the brim as otherwise you will always end up with slightly different amounts of fuel in the car.

I always fill up to the first "click" when the pump shuts off and try and use the same pump if possible

Chris

I use the on board computer to see realtime MPG. It's suprising that sometimes being in a higher gear doesn't automatically mean better MPG assuming it's accurate of course!

Try swapping gear at say cruising @ 40 mph in 6th, then change to 5th and then change to 4th! You maybe suprised at the result!

I use the on board computer to see realtime MPG. It's suprising that sometimes being in a higher gear doesn't automatically mean better MPG assuming it's accurate of course!

I believe it's all down to "throttle" position, so if you've changed up, but need more throttle to maintain a speed, then your economy will be lower, than if you were in a lower gear but using less throttle

Chris