Mpg discussion and mpg/vehicle range records

[Dunsignalling]

Dunsignalling

 

You got a good result, but the laws of physics favour super-super-slow.

 

The energy required to accelerate a body to a given velocity is half of the mass, times the velocity squared. To this must be added the energy that goes into warming the world up, through losses, some of which are proportional to velocity, some to velocity squared.

 

However, unless the vehicle has actually been designed for optimum energy efficiency which, as I observed before, practical cars aren't, it won't work well when running super-slow ....... it will probably stall, unless it has an automatic transmission, in which case it might crawl along at c2mph in tickover (my wife's car has VW DSG transmission, and that will).

 

The vehicles that demonstrate the physics to perfection are the ones used on solar-power endurance tests.

 

Kevin

Agreed, I think it was just a case of all the elements lining up just right on the day and, of course, it was over a fairly short distance. I doubt I could replicate it deliberately.

 

Interestingly, I have noticed that, even on normal days, returning Taunton-Honiton always returns worse consumption than the other direction, despite the "hilliness" presumably balancing out (or almost so).

 

My previous Peugeot (206 D Turbo 2.0 litre manual) seemed to have an anti-stall facility in the ECU (its first owner worked for the factory and it may not have been totally standard) which meant it would do a steady 10-12 mph in second (on a level road) without touching the throttle, whilst the trip computer indicated a fuel consumption approaching 100mpg.

 

John

Edited March 14, 2017 by Dunsignalling

[Nearholmer]

Messing about this morning, I got my car to run at a steady 10mph in second, which gave about 900rpm and 90-100mpg on a long, empty, straight, level road. I'm going to try similar in higher gears if/when I can find a suitable bit of road!

 

K

[brianusa]

Before coming to the US, in the UK, I always liked 'big' cars. Started of with a Vanguard, then a Velox and a Zodiac. Ever since arriving in the US, I've not worried about mileage. It was only a few cents then and not until the 70's petrol crisis did anything change; I turned in the big V8 Torino for a Mustang II. Now its about $3 something and as I don't do many miles, I still don't worry. My car gets about 18 mpUSg around town and 27 hywy. My wife's Acura gets about the same so mileage is still of no real concern!

 

My Dad used to write it all down religiously in a little notebook including oil use and servicing.

 

Brian.

Edited March 14, 2017 by brianusa

[Heinz57]

I drive a 2012 Ford Fiesta 1.8 Diesel Econetic. Yesterday evening I drove from my home in Ilkeston, just outside Nottingham to Yaxley, Peterborough. The route took me A52 to Grantham then A1. I set off with a full tank of fuel with the range calculator telling me the full tank will last me 320 miles. I arrived at Yaxley with the needle STILL on full with the computer telling me 405 miles of fuel. I'll admit I don't know the exact MPG I had during the trip, but I'll have to guess around 55mpg. This was with setting off at 4.30pm so hitting the A52 at peak time.

 

Strangley the return journy (which was about 10.30 depature) seemed to use a lot more fuel. I departed with the needle on the fuel guage just touching the full mark and arrived home dead on 3/4 of a tank remaining.

[How about a Dictator Loco Class?]

Before coming to the US, in the UK, I always liked 'big' cars. Started of with a Vanguard, then a Velox and a Zodiac. Ever since arriving in the US, I've not worried about mileage. It was only a few cents then and not until the 70's petrol crisis did anything change; I turned in the big V8 Torino for a Mustang II. Now its about $3 something and as I don't do many miles, I still don't worry. My car gets about 18 mpUSg around town and 27 hywy. My wife's Acura gets about the same so mileage is still of no real concern!My Dad used to write it all down religiously in a little notebook including oil use and servicing.Brian.

What litre is the Mustang?

 

Hahaha! My dad does the exact same thing. He has detailed records of every tank of fuel he's ever had and he does the same for me!

 

I'm often heading for 1,000miles to 1,200miles from a tank, but I have to fill up too early or do loads of fast journeys and short journeys and endless traffic jams! And my 76mile journey to work gets so flipping hilly!!! Grrr!

I'm back on for the 1,000 this month even though it's not that warm.

I was doing long journeys at near 100mpg last week too, which is early in the year to be getting that high mpg.

Annoyingly my current car's guage stops at 99mpg and the bar chart history logs at a mere 80mpg.

Fortunately my phone app and accurate fill up to fill up sums give the needed data.

Edited March 15, 2017 by How about a Dictator Loco Class?

[Guest]

Hahaha! My dad does the exact same thing. He has detailed records of every tank of fuel he's ever had and he does the same for me!

I used to use http://www.fuelly.com/ though I don't bother these days.

[Dunsignalling]

I drive a 2012 Ford Fiesta 1.8 Diesel Econetic. Yesterday evening I drove from my home in Ilkeston, just outside Nottingham to Yaxley, Peterborough. The route took me A52 to Grantham then A1. I set off with a full tank of fuel with the range calculator telling me the full tank will last me 320 miles. I arrived at Yaxley with the needle STILL on full with the computer telling me 405 miles of fuel. I'll admit I don't know the exact MPG I had during the trip, but I'll have to guess around 55mpg. This was with setting off at 4.30pm so hitting the A52 at peak time.

 

Strangley the return journy (which was about 10.30 depature) seemed to use a lot more fuel. I departed with the needle on the fuel guage just touching the full mark and arrived home dead on 3/4 of a tank remaining.

Sounds like a sticky float/sender in your tank. I had a car some years ago that would go well over 100 miles before the needle moved then similarly drop to three quarters in an instant.

 

Once it had done so, it worked fine over the rest of its range - I assumed the first owner never filled it right up so that end of the sender was stiff from disuse. It eventually stuck permanently and had to be replaced.

 

John

Edited March 15, 2017 by Dunsignalling

[jjb1970]

On our Golf the tank gauge seems to have a range between 10-90% of tank level as it take a while to start dropping and still has quite a lot left when it reaches zero. However there are no steps or stickiness between full and empty.

[Horsetan]

.... My dad does the exact same thing. He has detailed records of every tank of fuel he's ever had and he does the same for me!.....

I can see how people start to get obsessed by record-keeping, sometimes to the exclusion of everything else.

 

I remember reading about a Triumph TR4 (or possibly a 4A) that had been with the same owner since new. He had noted down, over the course of several ledger books, every single journey covered, every occasion the car was refuelled, every service it ever had and spare parts that were bought for it. You get the idea....

[Zero Gravitas]

I'm sad enough to have records of every tank of fuel for every car I have had since March 2000... from this I can tell you the best range I had was 885.4 miles (at a calculated 59.2 mpg) in a 2010 Volvo V70 in June 2012. The best tank mileage I have had is from my current 2016 Skoda Octavia Estate at a calculated 62.5 mpg over 396.6 miles.

[brianusa]

Before coming to the US, in the UK, I always liked 'big' cars. Started of with a Vanguard, then a Velox and a Zodiac. Ever since arriving in the US, I've not worried about mileage. It was only a few cents then and not until the 70's petrol crisis did anything change; I turned in the big V8 Torino for a Mustang II. Now its about $3 something and as I don't do many miles, I still don't worry. My car gets about 18 mpUSg around town and 27 hywy. My wife's Acura gets about the same so mileage is still of no real concern!

 

My Dad used to write it all down religiously in a little notebook including oil use and servicing.

 

Brian.

It was a Mustang 2, not one of the huge V8's of the day. It was built on a Pinto base and nobody liked them. Except me! It was under powered with a 2.2 litre engine and 4sp transmission so you had to turn off the A/C to help over long hills! But it lasted me nearly twenty years with 120K on the clock and no problems.

 

Brian.

[leopardml2341]

 

I suppose this will throw the proverbial cat, but my first experience of fuel computers in cars was the late 80's when the company I worked for used to hire in cars from iirc Godfrey Davis Ford Orion Ghia's and Rover 216 Vitesse. The challenge amongst employees was to get the lowest instantaneous and average figures. I attained 6 and 22 mpg resp.

 

Edit - added off topic warning

Edited March 15, 2017 by leopardml2341

[Red Baron]

I suppose this will throw the proverbial cat, but my first experience of fuel computers in cars was the late 80's when the company I worked for used to hire in cars from iirc Godfrey Davis Ford Orion Ghia's and Rover 216 Vitesse. The challenge amongst employees was to get the lowest instantaneous and average figures. I attained 6 and 22 mpg resp.

 

My old Mk1 Octavia vRS avg was 6mpg around the Nurburgring at full chat.....

[Horsetan]

....my first experience of fuel computers in cars was the late 80's ....

They'd been around since the early '80s at least. I had one in the 1983 635CSi, as part of the onboard computer. It wasn't pinpoint accurate, but it was close enough to be believable. Best figure I ever had for a trip was 40mpg, but it needed very gentle driving between London and York for that. Usual figure was 20 to 22mpg.

[Zero Gravitas]

Tediously, one of the statistics I monitor is the difference between the fuel computer figures and the real figures on a tank-by-tank basis.

 

The worst was the Volvo V70, which was, on average 5.1 mpg too optimistic (i.e. it was recording a figure 5.1 mpg better than actual) and the best was actually a Ford Fiesta, which was -0.5 mpg too optimistic (i.e. It was recording a figure 0.5 mpg worse than actual).

 

Generally, the trip computer is between 2 and 3 mpg too optimistic.

 

Yours sadly,

 

Z.G.

[37114]

I managed to get 70mpg out of an 05 plate Renault Megane 1.5 Diesel some years ago from Liverpool back to Chippenham. Current 140bhp 2.0 Mondeo averages 52.5 which amazes me as a) I have a lead right foot b) the last one I had averaged 42.8 so I am amazed Ford have managed to improve it that much.

 

Talking about range until empty, I left Chandlers Ford on Tuesday to drive the 67miles home with a range of 82 miles. All good on the Motorway/A303 as I am averaging 58mpg but get on to A360 and range starts dropping. I have a fuel card which I can only use in certain filling stations and by the time I was 10 miles from home range was only 9 miles. I pulled onto the forecourt having driven 2 miles with 0 range. I brimmed the tank with 58litres of diesel in what is supposed to be a 60 litre tank so am sceptical of how accurate the ranges are as on that basis I should have had another 20 miles to play with.

[Horsetan]

...Generally, the trip computer is between 2 and 3 mpg too optimistic.....

Isn't there supposed to be a 10% margin of error, like speedometers?

[Dunsignalling]

I managed to get 70mpg out of an 05 plate Renault Megane 1.5 Diesel some years ago from Liverpool back to Chippenham. Current 140bhp 2.0 Mondeo averages 52.5 which amazes me as a) I have a lead right foot b) the last one I had averaged 42.8 so I am amazed Ford have managed to improve it that much.

 

Talking about range until empty, I left Chandlers Ford on Tuesday to drive the 67miles home with a range of 82 miles. All good on the Motorway/A303 as I am averaging 58mpg but get on to A360 and range starts dropping. I have a fuel card which I can only use in certain filling stations and by the time I was 10 miles from home range was only 9 miles. I pulled onto the forecourt having driven 2 miles with 0 range. I brimmed the tank with 58litres of diesel in what is supposed to be a 60 litre tank so am sceptical of how accurate the ranges are as on that basis I should have had another 20 miles to play with.

Is it range till empty or range to reserve? Was your low fuel warning light not lit or only recently come on?

 

The one in my car activates when I've still got enough for fifty or so miles on board, which would fit in with what you apparently having a couple of litres in hand. 

 

Mind you, none of us would want it to work the other way round!

[Jol Wilkinson]

There are many factors thatb affect fuel consumption, besides the driving technique, although that is probably one of the most significant.

 

I rent my car as part of my retirement package and change it about every nine months, so I get first hand experience of some of the changes brought about through legislation, technology improvements, etc. The best fuel consumption I consistently got was on a 1.6L diesel fitted - as part of its standard spec - with  "economy" tyres. My current car, although a later Euro 6 spec. diesel has low profile tyres (rubber bands on big wheels) and is about 10% worse. Mind you we picked it up in January and driving in the wet conditions we had in the early months of this year also has had a detrimental affect.

 

Interesting comments about very low speed fuel consumption, I don't think any of my cars give a reading below 20mph, including the Peugeot 206 my wife had.

[Jol Wilkinson]

Is it range till empty or range to reserve? Was your low fuel warning light not lit or only recently come on?

 

The one in my car activates when I've still got enough for fifty or so miles on board, which would fit in with what you apparently having a couple of litres in hand. 

 

Mind you, none of us would want it to work the other way round!

Warning lights tend to come on with about 7L left in the tank. Makes you wonder why so many people still run out.

[PaulCheffus]

Hi

 

Lowest instantaneous mpg I've manged on my current car is 7mpg accelerating up hill.

 

Cheers

 

Paul

Edited March 16, 2017 by PaulCheffus

[Kickstart]

Isn't there supposed to be a 10% margin of error, like speedometers?

Not sure, but doubt it as there is no legal requirement on trip computers.

 

On speedos they are not meant to have a 10% margin for error. They can have a margin for error, which varies between classes of vehicles and it up to 10%+8kmh high.

 

All the best

 

Katy

[Adrian Wintle]

I track my mileage between fillups (brim the tank each time) and I find the best results are when I'm travelling in the US. I'm usually on cruise control on relatively empty Interstates at 65-75 mph (depending on the state and the prevailing speed limit).

 

Here are the best runs:

 

My current 2016 Subaru Crosstrek (XV) with a 2.0 normally aspirated petrol motor - 38.3 mpg (imperial gallons, not the undersized US ones)

 

My previous 2010 Subaru Impreza sedan with a 2.5 normally aspirated petrol motor - 40.0 mpg (less drag than the Crosstrek)

Lifetime (200900 miles) - 33.7 mpg

 

The 2002 Subaru Impreza wagon with a 2.5 normally aspirated petrol motor - 39.1 mpg

I don't have the lifetime figures but it was probably similar to the 2010 over its 205000 miles.

 

I don't have the records for the 1999 Subaru Impreza sedan with a 2.2 normally aspirated petrol motor, but its best was at least 39 mpg (for a more draggy car than the others), going over 500 miles on less than 60 litres of petrol.

 

The mpg displays on the 2010 and the 2016 are/were quite optimistic.

 

Adrian

Edited March 16, 2017 by Adrian Wintle

[37114]

Is it range till empty or range to reserve? Was your low fuel warning light not lit or only recently come on?

 

The one in my car activates when I've still got enough for fifty or so miles on board, which would fit in with what you apparently having a couple of litres in hand. 

 

Mind you, none of us would want it to work the other way round!

I think it is range until empty, the fuel light came on with 50 miles still left in the tank and as I drove warning messages came on progressively more frequently. 

[jjb1970]

A great popular misconception is that speedometers are set to read 10% high. The allowable margin of error is actually much more than 10% but this is not the same as setting a speedometer to be inaccurate, it means that the speedometer can read high (but not low) and still satisfy requirements for speedometer accuracy and approval. Most are set well within this tolerance, when out Golf reads 50mph the satnav indicates 48, my Citroen is similar to the Golf.