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Ways of describing fuel and electricity consumption
David Jenkins - 9/10/21 at 09:52 AM

Just wondering about people's views on this subject:

In an ICE car I think in miles per gallon (mpg) as a measure of fuel consumption. In my EV I think in miles per kilowatt/hour (m/kWh).

In Europe it seems that the ICE drivers think in litres per 100km, and EV drivers think in kWh per 100km.

I find it really hard to get a grasp of the European descriptions - I'm sure their method has its own advantages, but to me their way of describing fuel & electricity consumption seems... wrong.

What do you think?


ReMan - 9/10/21 at 10:14 AM

Agree, wrong! European wierdo's.

I'm sure a lot of it is 'how we were brought up',
but i don't see the advantage and sure doesn't picture well in my head.

mpg or even km per litre, I can picture how far I can get with my tank full, where the other methodss seems more biased to knowing how much its costing to run?


snapper - 9/10/21 at 09:21 PM

I look at it as mikes between per stops, if I have to fill up/charge before I need a pee the car is consuming to much go juice.
Clearly as my time goes by distance over bladder pressure reduces.


craig1410 - 10/10/21 at 12:46 AM

I think miles per gallon and miles per kWh are much better measures, mainly because the higher the number the better! It's sort of an optimistic view on the metric because bigger is better.

Litres per 100km and kWh per 100km are essentially inversely proportional to the above and as such, lower is better. I think this goes against most people's instincts when competing. It's partly why the BBC show "Pointless" is such a clever concept, because it goes against the normal means of competition where bigger is normally better.

Putting it another way - I think it's intellectually easier to try to achieve more miles per gallon/kWh than it is to consume fewer litres/kWh per 100km.

In a similar vein, although I tend to work in celsius mostly, I actually think that Fahrenheit is a better scale for humans to deal with when thinking about environmental conditions. Why? Because if you think about 0-100 in each scale. In celsius, 0 is fairly cold but we can handle much lower whereas 100C is almost certainly fatal. In Fahrenheit, 0F is getting towards the lower end of survivability and 100F is towards the upper end but neither are immediately fatal.


indykid - 10/10/21 at 07:32 PM

Despite the fact I instinctively have no frame of reference, I'd say the European way makes more sense. If you want to go somewhere and want to know how much fuel you'll use, it's a lot easier to get to both volume and cost if you work in volume/distance.

Fuel isn't sold in gallons anymore and multiplying by 4.546 isn't exactly easy to do in your head so using litres makes more sense.

As for temperature, if you're not using the Rťaumur scale, how the hell do you ever keep track?

[Edited on 10/10/21 by indykid]


craig1410 - 10/10/21 at 07:57 PM

Itís a fair point about litres vs gallons but I donít think Iíve ever gone to the fuel station having calculated exactly the amount of fuel I need to put in the tank for the journey Iím about to make. I almost always just fill up the tank. Probably the only exception to that would be if I was running low and had to fill up at an expensive fuel station in which case I would just buy enough to get me to a fairly priced one.

I know that aircraft pilots only put in enough fuel for a journey plus some contingency, but thatís due to the much bigger weight penalty for carrying excess fuel. In a 1.7T car like mine, it makes little difference if I carry an extra 25-30 Kg of diesel.

Also, since we mostly use miles in the UK, having to multiply by 1.609 isnít much fun either.

Perhaps we need a mix such as miles/litre or miles/10 litres.


ReMan - 10/10/21 at 08:33 PM

quote:
Originally posted by craig1410
Itís a fair point about litres vs gallons but I donít think Iíve ever gone to the fuel station having calculated exactly the amount of fuel I need to put in the tank for the journey Iím about to make. I almost always just fill up the tank. Probably the only exception to that would be if I was running low and had to fill up at an expensive fuel station in which case I would just buy enough to get me to a fairly priced one.

I know that aircraft pilots only put in enough fuel for a journey plus some contingency, but thatís due to the much bigger weight penalty for carrying excess fuel. In a 1.7T car like mine, it makes little difference if I carry an extra 25-30 Kg of diesel.

Also, since we mostly use miles in the UK, having to multiply by 1.609 isnít much fun either.

Perhaps we need a mix such as miles/litre or miles/10 litres.


Miles per litre would be a pretty depressing number, especially as we can't fail to know the current litre price as its lit up on the way into the station
ie 25mpg does not sound to bad and you don't know how much a gallon cost any more as above

But 5.4 Miles per litre sounds dire, when the current price is £1.30+ just to get to round the corner!


David Jenkins - 10/10/21 at 09:04 PM

quote:
Originally posted by craig1410
Perhaps we need a mix such as miles/litre or miles/10 litres.


It's a whole different topic, but I'd be more than happy to go entirely metric tomorrow, if the government finally decided to bite the bullet - but they never will as it's a quick way to lose votes. I've been to Australia many times, and I have absolutely no trouble coping with their metric system.


craig1410 - 10/10/21 at 09:06 PM

Might make people think whether to drive to the local shop or walk/cycle, which wouldnít be a bad thingÖ

Besides, 5.4 miles per litre is only about 24.5 MPG which is already pretty depressing IMO

The actual unit doesnít matter because whatever it is will become familiar in time whether itís 45MPG or 10MPL

@davidjenkins - yeah I agree but itíd be a costly exercise to redo all the road signs. I think most modern cars can switch unit on the speedo so no issues there. I already tend to use Kg for weights and NM for torque settings so switching to Km wouldnít be an issue for me. But Iíd still want Km/L rather than L/100km.

[Edited on 10/10/2021 by craig1410]


indykid - 10/10/21 at 09:32 PM

quote:
Originally posted by craig1410
Itís a fair point about litres vs gallons but I donít think Iíve ever gone to the fuel station having calculated exactly the amount of fuel I need to put in the tank for the journey Iím about to make. I almost always just fill up the tank. Probably the only exception to that would be if I was running low and had to fill up at an expensive fuel station in which case I would just buy enough to get me to a fairly priced one.

How do you decide how far is acceptable to drive to collect an ebay bargain or decide whether to pay the pallet courier price vs going to get it yourself?

Whatever the measure, it becomes an arbitrary comparator in one scenario or another. Having thought about it though, I maintain a usage based measure (volume/distance) needs less conversion in general than an output based measure (distance/archaic volume).

As a halfway house, perhaps we need to start using the calorific value of a gallon of fuel in kWh so we can have a direct comparison to EVs. We should probably adopt speed in furlongs/fortnight too.


craig1410 - 10/10/21 at 10:16 PM

quote:
Originally posted by indykid
quote:
Originally posted by craig1410
Itís a fair point about litres vs gallons but I donít think Iíve ever gone to the fuel station having calculated exactly the amount of fuel I need to put in the tank for the journey Iím about to make. I almost always just fill up the tank. Probably the only exception to that would be if I was running low and had to fill up at an expensive fuel station in which case I would just buy enough to get me to a fairly priced one.

How do you decide how far is acceptable to drive to collect an ebay bargain or decide whether to pay the pallet courier price vs going to get it yourself?

Whatever the measure, it becomes an arbitrary comparator in one scenario or another. Having thought about it though, I maintain a usage based measure (volume/distance) needs less conversion in general than an output based measure (distance/archaic volume).

As a halfway house, perhaps we need to start using the calorific value of a gallon of fuel in kWh so we can have a direct comparison to EVs. We should probably adopt speed in furlongs/fortnight too.


Iím not that scientific tbh, it comes down to how impatient I am to get my eBay purchase today and whether I feel like a drive. I work from home full time (even before Covid) so it doesnít take much to tempt me out for a drive.

Re the x/y or y/x thing, I just think we are hard wired to compete for the ďbigger is betterĒ outcome. Insert joke hereÖ


David Jenkins - 11/10/21 at 08:48 AM

quote:
Originally posted by craig1410
yeah I agree but itíd be a costly exercise to redo all the road signs. I think most modern cars can switch unit on the speedo so no issues there. I already tend to use Kg for weights and NM for torque settings so switching to Km wouldnít be an issue for me. But Iíd still want Km/L rather than L/100km.



The mish-mash that occurs with imperial measures really annoys me; I use Waze on my phone as my car's satnav, but that comes out with stuff like "In 1000 feet turn right" and I can't rapidly evaluate that distance in my head while driving - if it had said 300 metres or 300 yards I could relate to that instantly. My suspicion is that internally Waze is 'thinking' in metric, and the software is converting 300 metres into the nearest whole value in imperial.

Even more weirdly, my car has an altimeter (honestly - it's part of the compass!) that gives its value in yards... who measures altitude in yards!


James - 11/10/21 at 11:06 AM

quote:
Originally posted by David Jenkins
quote:
Originally posted by craig1410
yeah I agree but itíd be a costly exercise to redo all the road signs. I think most modern cars can switch unit on the speedo so no issues there. I already tend to use Kg for weights and NM for torque settings so switching to Km wouldnít be an issue for me. But Iíd still want Km/L rather than L/100km.



The mish-mash that occurs with imperial measures really annoys me; I use Waze on my phone as my car's satnav, but that comes out with stuff like "In 1000 feet turn right" and I can't rapidly evaluate that distance in my head while driving - if it had said 300 metres or 300 yards I could relate to that instantly. My suspicion is that internally Waze is 'thinking' in metric, and the software is converting 300 metres into the nearest whole value in imperial.

Even more weirdly, my car has an altimeter (honestly - it's part of the compass!) that gives its value in yards... who measures altitude in yards!


I'm fairly sure you can choose metric in Waze's settings.


James - 11/10/21 at 11:10 AM

quote:
Originally posted by James
[q


I'm fairly sure you can choose metric in Waze's settings.


Ah, I see.

Having now looked at the settings Of course, if you change to metric then the miles goes to kilometres. What you want is the map in miles but the alerts in metres.

Yeah, don't think you can mix and match sadly.


Mr Whippy - 11/10/21 at 11:23 AM

Just wait till you start with EV dashboard range estimates. The length of a mile seems to be vary by 50 - 200%


gremlin1234 - 11/10/21 at 01:05 PM

don't forget that american gallons are smaller than imperial gallons, making mpg even more confusing.


gremlin1234 - 11/10/21 at 01:08 PM

quote:
Originally posted by Mr Whippy
Just wait till you start with EV dashboard range estimates. The length of a mile seems to be vary by 50 - 200%
just like the old platform indicators on the 'northern line' which used their own system of flexible minutes.


coyoteboy - 11/10/21 at 01:53 PM

quote:
Originally posted by Mr Whippy
Just wait till you start with EV dashboard range estimates. The length of a mile seems to be vary by 50 - 200%


To be fair that's the same with my 370z - if I'm hooning through the hills my range is ~250 miles. 5 minutes later it can expand to 350+. Never had a car that was so inconsistent with fuel use - 18-20mpg in town, 36+ on a long motorway cruise.

[Edited on 11/10/21 by coyoteboy]


David Jenkins - 11/10/21 at 01:58 PM

quote:
Originally posted by James
I'm fairly sure you can choose metric in Waze's settings.


But I want my speed in mph!


David Jenkins - 11/10/21 at 02:00 PM

quote:
Originally posted by Mr Whippy
Just wait till you start with EV dashboard range estimates. The length of a mile seems to be vary by 50 - 200%


Especially in a Leaf - mine was shocking. My eNiro is pretty good with its estimates - only continuous 70mph driving will reduce it, and then only slightly.


scudderfish - 11/10/21 at 08:03 PM

I had a Mazda 6 where the onboard computer gave fuel consumption in litres per 100 miles....


nick205 - 12/10/21 at 12:26 PM

A rather lengthy thread to plough through this one!

I've only owned and driven ICE cars, petrol in my younger years then diesel for a long time. SWMBO has recently gone back to petrol. I tend to see it pretty simply as drive steady for better economy, drive heavy with he throttle and brakes for poorer economy.

Ultimately I measure it in terms of cost in £ for a tank of fuel vs miles travelled for that cost.

If I changed to EV or another energy I'd view it in much the same way.

Plus of course the cost and depreciation of the vehicle itself, irrespective of how it's powered.


chillis - 17/10/21 at 01:40 PM

The only effective comparison is cost per mile, however at the moment EV doesn't have any fuel duty applied so EV will currently appear cheaper to run, in the not too distant future there will be a charge (sorry for the pun) applied to recover the fuel duty lost to EV with the governments aim of ensuring no matter what the source energy that drives your vehicle is it will cost about the same per mile.