MPG or L/KM?

joujoujou · 01-06-2013 06:26PM

I wish we all have had only such big problems really. :P

I don't care what is best for him, for her, whatever.

I'm using litres per 100 kilometres myself, because I got used to.

If anyone else find other way is better for him/her - it's not my problem.

gizabeer · 01-06-2013 06:30PM

MPG all the way

YouTookMyName · 01-06-2013 06:30PM

Max Power1 wrote: »

I prefer miles per liter tbh

Sobanek · 01-06-2013 07:04PM

To the person that gave 8.9l/100km example.

What if my car does 37.3 mpg and I have 7.3 gallons in my fuel tank? Huh?

dgt · 01-06-2013 07:53PM

Sobanek wrote: »

To the person that gave 8.9l/100km example.

What if my car does 37.3 mpg and I have 7.3 gallons in my fuel tank? Huh?

Are you drunk again..... :pac:

Seriously, it was a silly statement to make, who knows whats in the tank till its drained and measured

CiniO · 01-06-2013 07:56PM

dgt wrote: »

Are you drunk again..... :pac:

Seriously, it was a silly statement to make, who knows whats in the tank till its drained and measured

Person who initially asked about 8.9 l/100km asked how much can you drive on 10 litres.
Who did he know there was 10 litres in the tank?

dgt · 01-06-2013 08:00PM

My point exactly, how would one know whats in the tank, pump and lines?

Sobanek · 01-06-2013 08:05PM

Some old cars like the BMW E32 actually tell you how much fuel you have:

dgt, that's the point I was making... How would I know how much fuel I have left, and how would he know he has 10 litres in his tank.

joujoujou · 01-06-2013 08:08PM

Sobanek wrote: »

Some old cars like the BMW E32 actually tell you how much fuel you have:

[...]

Some new ones actually can tell you how many kilometres/miles you can make on fuel you have in tank.

Anyway, it's an estimate only, as well as howmuchfuelyouhave thing.

Sobanek · 01-06-2013 08:15PM

joujoujou wrote: »

Some new ones actually can tell you how many kilometres/miles you can make on fuel you have in tank.

Anyway, it's an estimate only, as well as howmuchfuelyouhave thing.

Even the car above has "Range" in its computer

CiniO · 01-06-2013 08:23PM

dgt wrote: »

My point exactly, how would one know whats in the tank, pump and lines?

So in general, you mean there's more often a need to know how much fuel you need to travel certain distance, than knowing how much distance you can travel on certain amount of fuel. At least that what I undestand concludes what you meant.

And if so, l/100km is way better measurement for calculating amount of fuel needed for certain distance than mpg or km/l.

It really makes sense.
How many people wake up in the morning, and think to themselves - I've got 4 gallons of fuel in my tank. My car does 40MPG. So I can travel 160miles. Therefore I can go to Cork and back today, as it's only 78 miles to get there.
I'd say not many.

Most people wake up in the morning, and think to themselves - I need to get to Dublin and back today. It's 300km each way, so I need to travel 600km.
My car does 6 l/100km, so I'll need 6*6 = 36 litres of fuel. Then you go to petrol station, fill'er up by 36 litres and off you go to Dublin.
This makes perfect sense.

HandsomeDan · 01-06-2013 08:29PM

CiniO wrote: »

Most people wake up in the morning, and think to themselves - I need to get to Dublin and back today. It's 300km each way, so I need to travel 600km.

That's unbelievable! That's exactly what I thought this morning. And I wasn't even going to Cork today?

dgt · 01-06-2013 08:40PM

Zut alors! My tiny brain is fried here.....

I fill up with what I estimate I'll need for the next week. Good planning and all that. I rarely get caught out too

I work with mpgs as its what works for me, what I'm used to. I know what I have, estimate my range and work with a small margin of error. Why should I change what works for me?

To confuse things further I work with time and not distances. I look at a sign with 20kms distance left and est my time of arrival at about 15 mins at 80 kmh constant, realistically 20 accounting for numpties, braking and other external forces.

Don't try change me, I'm stuck in my ways. What most people do I'll usually rebel against it anyway

HurtLocker · 01-06-2013 08:54PM

I'm thrown between the two. I use L/100km the dash for current consumption but when I use the Road Trip app I leave it on MPG. I don't know why it makes sense to me. Although I keep an idea in my head of €/km so I've an idea of how much fuel I've used and how much it'll cost me to refill. Nice easy to remember €0.10 per km at the moment.

Mandzhalas · 01-06-2013 08:56PM

road signs shows distance in kilometers
petrol stations pumps shows amount in litres
car speedos displays in km/h (from 2004)
why on earth use mpg???

Jesus. · 01-06-2013 09:10PM

joujoujou wrote: »

Some new ones actually can tell you how many kilometres/miles you can make on fuel you have in tank.

Funny you should mention that, joujoujou, I've got one of those settings on my new (10 yr old!) Motor. I've only had the car two weeks so I only had the petrol down low once. That setting showed about 70 miles left in the tank before I ran out but when the "fuel up" light came on, that setting disappeared.

Why wouldn't it continue giving me estimates just cos the fuel light came on?

TheChizler · 01-06-2013 09:17PM

Poster up above hit it on the head, when starting a journey the distance you need to go is fixed, you want to know if you have enough fuel to cover that fixed amount. You don't pick your destination based on how much fuel you have. Volume of fuel per distance makes sense in this context.

Even if you have the wrong one a quick estimate in your head is good enough, the efficiency/consumption is going to be changing constantly anyway so even if you use a calculator it's going to be nowhere near accurate.

_Kaiser_ · 01-06-2013 10:11PM

This may be useful for some.. MPG to l/100 km converter

evolutionqy7 · 01-06-2013 10:26PM

L/100 km

Kind awkward to work out liters into gallons and then kilometers into miles.

Metric is more straight forward for me anyway

BMJD · 01-06-2013 10:43PM

I don't give a hooting hoot how far my upcoming journey is! If it's nearly empty, I fill 'er up, end of.

Jesus. · 01-06-2013 11:18PM

TheChizler wrote: »

Poster up above hit it on the head, when starting a journey the distance you need to go is fixed, you want to know if you have enough fuel to cover that fixed amount. You don't pick your destination based on how much fuel you have. Volume of fuel per distance makes sense in this context.

Even if you have the wrong one a quick estimate in your head is good enough, the efficiency/consumption is going to be changing constantly anyway so even if you use a calculator it's going to be nowhere near accurate.

Cheers man. I didn't even know I'd said all those things!!

dr.fuzzenstein · 02-06-2013 12:13AM

Sobanek wrote: »

To the person that gave 8.9l/100km example.

What if my car does 37.3 mpg and I have 7.3 gallons in my fuel tank? Huh?

Then you must like dealing with arbitrary and outdated medieval measurements. Example below is US but you get the idea...

l/100km makes all the sense in the world and it takes me 30 seconds to work out when filling up my car, but only because I'm slow at math!:p
I simply could not take the liters I filled up and the kmI have driven, convert them to gallons and miles AND work out my MPG. A lot of people here like pain it seems.

Chris_Heilong · 02-06-2013 12:35AM

Miles are for losers, get with the times....only joking but because everyone uses MPG here so do I but only for measuring fuel, every thing else is Kg, meters and Km per hour.

djimi · 02-06-2013 07:45AM

CiniO wrote: »

So in general, you mean there's more often a need to know how much fuel you need to travel certain distance, than knowing how much distance you can travel on certain amount of fuel. At least that what I undestand concludes what you meant.

And if so, l/100km is way better measurement for calculating amount of fuel needed for certain distance than mpg or km/l.

It really makes sense.
How many people wake up in the morning, and think to themselves - I've got 4 gallons of fuel in my tank. My car does 40MPG. So I can travel 160miles. Therefore I can go to Cork and back today, as it's only 78 miles to get there.
I'd say not many.

Most people wake up in the morning, and think to themselves - I need to get to Dublin and back today. It's 300km each way, so I need to travel 600km.
My car does 6 l/100km, so I'll need 6*6 = 36 litres of fuel. Then you go to petrol station, fill'er up by 36 litres and off you go to Dublin.
This makes perfect sense.

You know both calculations are exactly the same, right? You wake up in the morning and decide to do a 300km journey then working out that your car does 30km/l so you'll need 10 litres is exactly the same as saying that your car does 3l/100km so you will need 9 litres. There is literally no difference in the calculation!

For me km/l seems a lot more natural. For years people thought in terms of mpg, so km/l is the natural progression of that. L/100km just seems like an odd and strangely unnecessary way of calculating fuel mileage.

Mr.David · 02-06-2013 12:19PM

mpg is a terrible, terrible measurement!

its not linear and therein lies its massive flaw. moving from a 10mpg car to a 20mpg car saves you more fuel than moving from a 20mpg car to a 100mpg car.

sound stupid? yes!

l/100km however, is linear.

the impact of this is that the benefit of increasing your mpg declines exponentially. so, the fuel saving of running a 50mpg vs 40mpg car is very minimal, whereas 10 to 20mpg is massive.

djimi · 02-06-2013 12:26PM

Mr.David wrote: »

mpg is a terrible, terrible measurement!

its not linear and therein lies its massive flaw. moving from a 10mpg car to a 20mpg car saves you more fuel than moving from a 20mpg car to a 100mpg car.

sound stupid? yes!

l/100km however, is linear.

the impact of this is that the benefit of increasing your mpg declines exponentially. so, the fuel saving of running a 50mpg vs 40mpg car is very minimal, whereas 10 to 20mpg is massive.

Can you explain this in a bit more detail please? Im failing to see the difference.

CiniO · 02-06-2013 12:55PM

djimi wrote: »

You know both calculations are exactly the same, right? You wake up in the morning and decide to do a 300km journey then working out that your car does 30km/l so you'll need 10 litres is exactly the same as saying that your car does 3l/100km so you will need 9 litres. There is literally no difference in the calculation!

For me km/l seems a lot more natural. For years people thought in terms of mpg, so km/l is the natural progression of that. L/100km just seems like an odd and strangely unnecessary way of calculating fuel mileage.

Obviously both can be used to calculate the same thing.

But hence that l/100km shows how much fuel you'll need to travel certain distance.
km/l shows how much distance you can travel on certain amount of fuel.

People in vast majority of cases need to know the first thing (how much fuel you'll need to travel certain distance).

It's just easier for calculations then.
You take your consumption f.e. 7.4 l/100km and multiply it by amount of 100s of kilometres you want to travel. So f.e. you want to travel 250km, then it's 7.4*2.5 = 18.5 litres. That's calculation I was able to do in my head within few seconds, even though both factors contains fractions.

7.4 l/100km is 13.5 km/l. If you want to travel 250km, you need division. 250 / 13.5 = ???? We already know it's 18.5 litres, but that's not the calculation I car do easily in my head.

Your example made it equally easy as you just choose adequate amounts. I chose random amounts, and you can see it makes a difference.
Multiplying in your head is way easier than dividing.

Besides - if Irish people are to convert from imperial units to metric units, why do it the wrong way? I mean why create an unit like km/l which probably isn't used anywhere in the world while you can just use l/100km which is used nearly everywhere. Doesn't make sense.

CiniO · 02-06-2013 01:02PM

Mr.David wrote: »

mpg is a terrible, terrible measurement!

its not linear and therein lies its massive flaw. moving from a 10mpg car to a 20mpg car saves you more fuel than moving from a 20mpg car to a 100mpg car.

sound stupid? yes!

l/100km however, is linear.

the impact of this is that the benefit of increasing your mpg declines exponentially. so, the fuel saving of running a 50mpg vs 40mpg car is very minimal, whereas 10 to 20mpg is massive.

While I agree that MPG is not good measuerement, but I can't get your point.
It is linear.
If your car does 10mpg and mine does 20mpg, that mean your car will use twice amount the fuel for the same distance.
If your does 20mpg and mine does 100mpg, then your car will use 5 times the amount of fuel as mine.

Exactly the same like with l/100km.
If my car does 10l/100km and yours does 20l/100km, then your uses twice amount of fuel as mine.

HandsomeDan · 02-06-2013 02:29PM

CiniO wrote: »

While I agree that MPG is not good measuerement, but I can't get your point.
It is linear.
If your car does 10mpg and mine does 20mpg, that mean your car will use twice amount the fuel for the same distance.
If your does 20mpg and mine does 100mpg, then your car will use 5 times the amount of fuel as mine.

Exactly the same like with l/100km.
If my car does 10l/100km and yours does 20l/100km, then your uses twice amount of fuel as mine.

I think he's just demoing the unintuitiveness of the mpg rating. For any given journey the difference in the amount of fuel used by a 10 and 20 MPG car is greater than the difference between a 20 and 100 MPG car.

This would be more obvious using the l/100km rating i.e. 2l/100km 10l/100km & 20l/100km - I've not converted directly here, but the ratios are the same.

In a nutshell ,l/100km is directly proportional to consumption, and MPG is inversely proportional - the difference really lies in what you're used to or not.

02-06-2013 05:17PM

MPG all the way. Hate the sight of l/100km. It's very annoying that I can't change the read out on my car to mpg as I'm always having to convert. Basically l/100km means nothing to me but I can instantly visualise mpg.

Same for speed, my speed odometer is in km but I constantly convert to mph in my head or when I look at a speed sign I convert it to mph etc.

MPG or L/KM?

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