Fuel consumption and speed

peasant

For a few months now, I've got a new route into work, 30 odd km each way. A bit of dual carriageway, a bit of good straight single carriage, a bit of town traffic and a lot of severe bends and long inclines.

My van (for those that don't know it) is underpowered, heavy and about as aerodynamic as a hay barn.

For the first few weeks I've driven that route with "gusto" ...100 + on the straights and really laid into the bends in a "sporty" style (as much as that is possible with my yoke).
Fuel consumption ...a fairly frightening 9.5 - 10 l/100 km

Then came the winter, with lots of ice, snow and over-cautios drivers and I found myself trundling home (usually behind someone else) at 40 - 60 all the way for several weeks and more than one tank ...fuel consumption ...an astonishing 6.5 -7 l/100 km.

After that wake-up call (and considering current fuel prices) I changed my style from push to glide. ~ 90 on the straights and a smooth style through the bends with just engine braking and gentle acceleration. Journey takes about 1-2 mins longer than when pushing it ...but the last tank full showed a fuel consumption of 8.2 l/100 km.

That's around 130 km (or almost 2 x to work and back) per tank extra with no perceptible time loss and without being an obstacle to other drivers.

Often try and do similar but about a mile into my journey I can't resist the aural V6 symphony.

kerten

This is the case for all vehicles. I think it becomes more visible for vans due to aerodynamic disadvantage, short geared high torques low ps diesel engines especially when they don't have a turbo.

Steady speed for all road is the best unless it is less than 50 km/h for back roads.

Over 80 km\h any car will have less economy. my car gives mpgs below on steady speed on motorway from obc which is same to brim to brim measurement

80km/h - 45 mpg
100 km/h - 38 mpg
120 km/h - 34 mpg

I can do between 27-45 mpg on same road depends how granny I am.

Mycroft H

peasant wrote: »

For a few months now, I've got a new route into work, 30 odd km each way. A bit of dual carriageway, a bit of good straight single carriage, a bit of town traffic and a lot of severe bends and long inclines.

My van (for those that don't know it) is underpowered, heavy and about as aerodynamic as a hay barn.

For the first few weeks I've driven that route with "gusto" ...100 + on the straights and really laid into the bends in a "sporty" style (as much as that is possible with my yoke).
Fuel consumption ...a fairly frightening 9.5 - 10 l/100 km

Then came the winter, with lots of ice, snow and over-cautios drivers and I found myself trundling home (usually behind someone else) at 40 - 60 all the way for several weeks and more than one tank ...fuel consumption ...an astonishing 6.5 -7 l/100 km.

After that wake-up call (and considering current fuel prices) I changed my style from push to glide. ~ 90 on the straights and a smooth style through the bends with just engine braking and gentle acceleration. Journey takes about 1-2 mins longer than when pushing it ...but the last tank full showed a fuel consumption of 8.2 l/100 km.

That's around 130 km (or almost 2 x to work and back) per tank extra with no perceptible time loss and without being an obstacle to other drivers.

Whats that in MPG :P

Can't understand liters per 100km things

-Corkie-

I was talking to the owner of a fairly large transport company last week and he is limiting all the trucks to 80KPH, previously 91KPH. He has some done and they are returning 2-3 MPG which is a massive saving on a truck. It would be 40-50 litres a day...

650Ginge

www.fuelly.com......

track your mpg and be disgusted by how much it costs.....but you are better to know and make an informed decision...it is amazing how some people who have no idea what mpg they are getting.....girl in work thinks she is get 45 for her astra, we worked it out the other day roughly she is getting 33mpg....

OP you are late to the recognition that speed costs more in petrol, accelerating from corner to corner will really reduce your mpg and significately increase the amount of money that you spend on motoring each year and you most times wont make any time.....cause up the road you will come across me doing 55-60mph and I never hit the hardshoulder so you can overtake.....if you want to overtake you got to wait for a gap.

peasant

650Ginge wrote: »

OP you are late to the recognition that speed costs more in petrol...

Not exactly ...I knew all the time ...I just didn't care

Before I got this job, one tank lasted me almost 2 months ...these days that's down to under 2 weeks ...something had to give. :mad:

Iwannahurl

I found these docs while searching for info to use in another thread. Worth a look I believe.

Save as you drive: background information for expert fuel savers

PRIMER ON AUTOMOBILE FUEL EFFICIENCY AND EMISSIONS

Obviously it's well worth being tuned into your vehicle's fuel consumption and aware of ways to keep it to a minimum.

However, I was shocked to discover that a vehicle powered by an internal combustion engine is only around 15% efficient -- I knew it was bad, but not that bad.

The corollary is that 85% of fuel is consumed in ways that do not help you get from A to B. Kinda puts efforts at fuel economy into perspective. Still, every little helps.

650Ginge

15% is shocking for sure......

Just a question but in the context of an electric car, what is the efficiency of
a./ the car

and

b./ an electric power station

Seth Brundle

I've recently lightened my right foot along the N4/M50 commute and timewise, I'm not losing much but am not as stressed when I arrive and my economy has imrpoved quite a bit.
I'll give it another week and let you know how much of the planet I've saved.

I am usually either just in time for my 8.30 meeting or late, I reckon if I left earlier the lighter traffic would improve my mpg a bit. So hard to get out of the leaba (bed) in the morning.

Matt Simis

I dont care for (and dont dispute) the fuel savings, I have too far to drive to mentally accept making less than swift progress. Id simply go mad.
This is why I cannot drive the diesel into work either.

I was considering removing spare wheel and anything similar to save weight though, performance through lightness sounds more my angle.

-Chris-

I've just never been able to do it.

I've tried to drive more gently, to be calm, to conserve fuel. I really have!

Most of the time I just feel like this (substitute feet for hands, of course):

coylemj

I'd drive the odd time to Athlone, it's never during peak commuting time so the towns along the way are relatively traffic-free. If I drive down the M4/M6, I have to pay 2.90 toll each way and I end up driving at 110-120 km/hr.

If I drive the old road through the towns I find that I drive at about 80 kms/hr most of the way but obviously have to slow to 50 or 60 in the small towns. Result: I save a fortune on fuel and tolls and I avoid the risk of falling asleep from the boredom that goes with driving along a featureless motorway.

coylemj

coylemj wrote: »

I avoid the risk of falling asleep from the boredom that goes with driving along a featureless motorway.

Oh the memories, I used to drive from Dublin to Cork years ago twice a month after a 12 hour nightshift.

Absurdum

650Ginge wrote: »

15% is shocking for sure......

Just a question but in the context of an electric car, what is the efficiency of
a./ the car

and

b./ an electric power station

very roughly..

a. 30-35%

b. 70%+

both can vary hugely....

OldmanMondeo

650Ginge wrote: »

15% is shocking for sure......

Just a question but in the context of an electric car, what is the efficiency of
a./ the car

and

b./ an electric power station

I was watching fifh gear when the tested the Nissan Leaf, basically what they said was, when you take everything into account, ie making the car, making the electricty, moving the oil etc, the EV work out a hell of a lot more efficent and enviromently friendly than an oil burner... As regards a fill up, a 60 ltr diesel will cost around €90 to fill, getting say 700 miles, a EV will cost about €2 to fill up and get around 150 miles. so to match a diesel you would save around €80 every time. Dam I wish they were real life ready...

OldmanMondeo

Matt Simis wrote: »

I dont care for (and dont dispute) the fuel savings, I have too far to drive to mentally accept making less than swift progress. Id simply go mad.
This is why I cannot drive the diesel into work either.

I was considering removing spare wheel and anything similar to save weight though, performance through lightness sounds more my angle.

Weight is a big factor as well. I had 4 adults and 4 kayaks on the roof, plus all the gear required in the boot. My mpg drop from a display of 48mpg to 37mpg. Than was on a 300 mile trip on a motorway way at around 120kph.

Iwannahurl

650Ginge wrote: »

15% is shocking for sure......

Just a question but in the context of an electric car, what is the efficiency of
a./ the car

and

b./ an electric power station

Here's an informal paper suggesting that "the power-plant-to-wheel or wind-farm-to-wheel efficiency of an electric car with regenerative braking" could be as much as 66%. If electricity generation is to be done using renewable and sustainable methods then the future of motoring is electric.

I cannot afford to fill the petrol tank as often as I used to. I don't know how else to economise, so my preferred mode of transport for manageable short distances is Shank's Pony or else the most energy-efficient mode of travel ever invented.

Matt Simis

OldmanMondeo wrote: »

Weight is a big factor as well. I had 4 adults and 4 kayaks on the roof, plus all the gear required in the boot. My mpg drop from a display of 48mpg to 37mpg. Than was on a 300 mile trip on a motorway way at around 120kph.

Thats actually a minimal drop considering the weight and massive wind resistance you describe. Which means Id save virtually nothing by clearing out the boot.

Joe 90

OldmanMondeo wrote: »

I was watching fifh gear when the tested the Nissan Leaf, basically what they said was, when you take everything into account, ie making the car, making the electricty, moving the oil etc, the EV work out a hell of a lot more efficent and enviromently friendly than an oil burner... As regards a fill up, a 60 ltr diesel will cost around €90 to fill, getting say 700 miles, a EV will cost about €2 to fill up and get around 150 miles. so to match a diesel you would save around €80 every time. Dam I wish they were real life ready...

Although on a pure cost basis you are not really comparing like with like as about two thirds of the cost of the diesel is tax.

Idbatterim

I drive down to athlone the odd time and sometimes on the way back I used to dodge the motorway, but when I consider the poor roads through the villages, and the damage to the suspension, bushings, control arms etc! I dont think dodging motorway is a wise investment anymore!

biko

For me it's all about city vs country driving.
All city driving - 350 miles to a tank
All country/motorway - 450 miles to a tank.
Massive difference. This seems to be standard for older E36.

SouperComputer

City driving, mass of the vehicle & engine size come into play the most. Larger engine will typically use more fuel idling.

Motorway driving aero is the biggest factor, provided the trip isnt crazy hilly. Weight\mass changes (withing reason) make little difference to cruising consumption. Engine size isnt nearly as big a factor as you might think.

RoverJames

RoverJames wrote: »

Often try and do similar but about a mile into my journey I can't resist the aural V6 symphony.

Filled her up this evening and thought of this thread, I shall try and keep it below 3000/3500rpm and only accelerate gently and see is there any difference in mpg. Won't be easy me thinks

robtri

peasant wrote: »

Not exactly ...I knew all the time ...I just didn't care

now thats the right attitude

Eph1958

peasant wrote: »

My van (for those that don't know it) is underpowered, heavy and about as aerodynamic as a hay barn.

For the first few weeks I've driven that route with "gusto" ...100 + on the straights and really laid into the bends in a "sporty" style (as much as that is possible with my yoke).
Fuel consumption ...a fairly frightening 9.5 - 10 l/100 km

Hi, do you mind me asking model and engine size of van? I drive a VW transporter and new model seems a bit more thirsty than previous ones. I could get 7.5l/100km average and about 6.2l/100km long journey on previous model but this year it's up to about 8.5 & 7.5 respectively.