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My Mondeo diesel at 85mph indicates approx 47.5mpg at 70mph about 49.5mpg. Over 50 miles I prefer to get home quicker than save a bit of fuel.
I would suggest one or both of these figures are inaccurate. A 21% in crease in speed for only a 4 % increase in fuel would be a marvel of engineering. Unless the efficiently of you engine improves massively in the range 70 - 85 mph I don't think it is possible.
off in people going out for a scenic run in their car at the weekend
I think that happened in the 60's?
I drove to work this morning, not because of some addiction but becasue I just couldn't be bothered to cycle. A day's petrol is probbaly £4?
Other things I'll spend more on today......
Bike parts or bike related tat - just bought a portable 'jet' wash
Food - do I need to spend £4 on steak when 99p value mince is essentialy the same, or even 25p of when protein?
Bessides, I like the smell of petrol almost as much as I like the smell of steak and burning break pads 🙂
Unless the efficiently of you engine improves massively in the range 70 - 85 mph I don't think it is possible.
Hmmm, mines a bit like this as well though.
65mph - 55mpg
75mph - 45mpg
85mph - 48mpg (which does surprise me)
So it's cheaper to go faster (or slower)......
Don't know why it does this - gear ratios, revs, dunno.
DrRS**** - Member
Unless the efficiently of you engine improves massively in the range 70 - 85 mph I don't think it is possible.
Hmmm, mines a bit like this as well though.65mph - 55mpg
75mph - 45mpg
85mph - 48mpg (which does surprise me)So it's cheaper to go faster (or slower)......
Don't know why it does this - gear ratios, revs, dunno.
I think the computer is lying to you. Something in inaccurate.
Very roughly the drag on a object moving through the air is proportional to v^3 where v is the velocity.
So increasing the velocity by 13.33% (10/75) would result in 69 % more fuel being used.
If we let you engine be x_1% efficient at 75 miles an hour with a given fuel energy density d then the energy available to us at 75 mph and needed to move the car one mile
E(75)=(1/45)*d*(x_1/100)
now at 85 mph we will assume an efficiently of x_2% we have
E(85)=(1/48)*d*(x_2/100)
energy available to us, which also must equal the amount of energy to move one mile at 85 mph.
We know that the energy required to move at 85 mph is 68% more than at 75 mph so
E(75)*1.68=E(85)
(48/45)*1.68*x_1=x_2
1.79*x_1=x_2
So your cars efficiency would have to improve by 79% at 85 mph than at 75.mph.
E.g it was 31% efficient at 75 mph and it becomes 55.5% efficient at 85 mph.
To gain this must efficiently would be amazing, and for a manufacture to place that imprisonment in efficiency in the range 75-85 mph, when cars are sold on urban mpg and extra urban mpg of 62 mph would be very strange.*
*Unless I have made some very silly mistakes.
[i]Supply and Demand innit [/i]
Why would that change the price?
*Unless I have made some very silly mistakes.
just wondering if 6 gears makes a difference here?
I don't think it could account for the massive increase in efficiency. I'm not sure how efficient engines are but I bet it's not very with all that heat being blown out.
Until public transport becomes cheaper and a nicer way to travel then people will continue to use cars :uber fact:
Diesel would have to rise to £3.10/litre before it would cost me the same to drive as it would to use South West Trains for my daily commute.
And that's not taking into account the benefit of not sharing a space with window lickers and people with no concept of social etiquette.
Oh and the Libya/North Sea thing is surely just profiteering when boiled down.
sharkbait - MemberSo we should all live in cities then?
I don't live in a city but I've got a train service (crap) and a bus service (decent) which I can use to get to an international airport and national train links. Plus local mini supermarket, off licence, butcher, post office. I own a car but only for convenience and for biking.
It's a big step from "I live in the country in the arse end of nowhere" to "I live in a city", that should be pretty obvious.
Drive at 85mph, take your foot off the accelerator and voila, 100+mpg - you cant give accurate MPG unless you average a large number of miles.
I'm sure the fuel prices have affected the way people drive their cars already. I'm not talking about driving to work and shops etc, I'm talking about leisure driving. I'm sure the price of a journey around the country roads, or trips to friends houses is taken into account more now that the prices of fuel are so high.
Also number of cars per household may well be dropping. We went 1 car about 4 years ago. I know of a couple of mates who have done the same since
Even if petrol were free, I don't think many people would actualy WANT to drive 100 miles each way for work, so that is something we can work with.
I think many people don't care how far they drive.
A mate of mine commutes 42 miles (over an hour) each way every day and has done for about 15 years. He has (he readily admits) a fairly dull job (he worked in a room with no windows for 10 years!) but has made no effort in all that time to find anything else closer to home, despite living in a city and commuting out every day.
In fact he looks forward to the hour he spends in the car as a stress free hour away from family life (2 small kids) and work to listen to music.
Now, I don't blame him for feeling like that, but it is a pretty sad state of affairs really.
Similarly my wife commutes 16 miles each way to work as a teacher, while another teacher she knows is at the same time commuting in the opposite direction! Madness. But that is what has happened because of our historical disregard for the value of oil - instead of treating it as a precious and finite resource we've been completely gung-ho in the way we use it.
Personally, I think that if we take this current crisis as a hint to start to give a bit more thought to the way we organise ouselves now it might do us all a favour in the long run.
It took the planet 100 million years to turn all that energy into oil. The Human race will burn through it in a few hundred years. Cars, trains, planes, domestic heating, it's all just ridiculously unsustainable.
10MPG or 100 MPG, it doesn't make any difference...we are going to use it all up in no time regardless, and will have to live with the consequences.
I am totally part of it, and so are you.
There is no answer. Just enjoy it while it lasts.
As an addendum...The only people I know personally who do not pollute the planet are on the Dole. Flat broke, carless, and pitied by society.
Diesel would have to rise to £3.10/litre before it would cost me the same to drive as it would to use South West Trains for my daily commute.
Except that by then the wider social/economic effects of fuel at that price would have thrown the country into turmoil. Maybe you wouldn't have a job anymore to commute to?
Drive at 85mph, take your foot off the accelerator and voila, 100+mpg - you cant give accurate MPG unless you average a large number of miles
Duh. That's the instant mpg. Press the button to switch to AVERAGE mpg since the last time you reset it 🙄
There is no answer. Just enjoy it while it lasts.
Yes there is. Reduce the amount of journeys we have to make until we can power them all via sustainable means.
Re cars being more efficient as they get faster - there is some basis for this although I too dispute the actual values discussed here.
Both petrol and diesel engines are more efficient at wider throttle openings, but for different reasons. I've heard people report slightly higher mpg at 80 than 70 but only in huge petrol engined cars with stupidly high gears (ie big American ones).
18,854 miles is about 429 return journeys which means that it would still, at £1.40 a litre, be much cheaper for me to drive (I don't I get the train).
Well yeah but only if you have a car anyway - depreciation, road tax, insurance - and then there's wear and tear for the miles you would do - parking too probably. Cheaper to get the train.
"Why would that change the price?"
On Radio 4 last night they were talking to lots of foreign national oil people trying to get out of Lybia asap as gunmen were running riot through their drilling sites.
So Libian oil production drops = less oil available in the world = north sea oil can be sold at a higher price.
I commute 100 miles per day and tbh petrol would have to triple in price to equal an hours pay, and thats in my gas-guzzler - so no brainer for me.
I commute 100 miles per day and tbh petrol would have to triple in price to equal an hours pay, and thats in my gas-guzzler - so no brainer for me.
"no brainer" - are you saying that you don't mind spending 2 hours sitting in your car + and wouldn't mind spending another hour working to pay for the privilege, every day?
I also consider that a "no brainer" but I have the opposite view to you.