…more difficult to measure?
Fuel companies would make less money from us?

F1 is a weight weenie sport.

It is convention to measure liquids by volume not weight
Can you name another example where a liquid is sold by weight rather than volume?
Bet there is something but nothing springs to mind instantly

What’s the point? You know your tank is 60 litres, that’s how much fuel will go in it.

It might be equivalent to 48kg of diesel, but that means you have to know the fuel’s specific gravity to know how much to put in. Temp etc all plays a part in this.

Temp etc all plays a part in this.

That’s why in theory we should buy per kg. 1 litre of fuel at 25°C contains less mass and therefore less energy than 1 litre at 5°C

In practice, it probably makes three-quarters of bugger all difference.

The point is, a given mass of fuel may have more or less volume depending on the temperature of the fuel as the fuel becomes less dense as it heats up. So if you fill up first thing in the morning when the fuel will be at its coolest, you will get more fuel (by weight) than if you filled up in the evening. Whereas if it was sold by weight, you would always get the same amount of fuel.

EDIT: too slow again!!

as it is stored underground I very much doubt there is any real variation in the temp of the fuel delivered. As liquids heat up they expand as well – see a thermometer for example – so same difference so to speak. Perhaps they put the fuel in at certain temp in F1 to be super accurate to ensure it reaches the end?

When transporting bulk fuel the orders are usually made up in tonnages, however when the bills of laden go on board the ship they are calculated with density and m3 (usually in air @15 degrees). confused? you are now. 😆

I believe aircraft measure fuel by weight.
Also, electronic fuel injection systems calculate the amount of fuel to inject by weight or mass.
The air flow meter measures the mass of air coming in to the engine and the ECU uses information from a fuel temperature sensor to calculate how long to hold the injector open to get the correct fuel/air ratio.

LPG is sold by volume for vehicle use from a pump.
LPG (propane or butane) is sold by weight in cylinders.

Even in underground tanks you can have temperature variations that will change the volume of the liquid(s) present, so you should do the temperature calculations whenever you take a dip to ensure accuracy over the year (as well as meauring the water present). A recent delivery may dramatically alter that temperature, so it does fluctuate.
Aircraft calculate their fuel by weight as that is the important figure on an aircraft – aircraft + load + fuel + weather + altitude will be a factor on the max weight the aircraft can take off at.

F1 fuel calculations will be more complex again – and vary for each engine.

I suspect that volume changes related to temperature are a lesser effect compared to the change in the evaporation rates of the nice volatile bits of the the fuel that give it the vavavroom.

Not really much difference between F1 fuel and norml car fuel – just tighter mixes and within tight limits. Everything is so fine in F1 that there in’t any part of the car that is not relevant to performance, so ensuring the balance between weight carried and fuel stopped for is critical, as well as performance from the fuel itself.

Martin Brundle explained during the race that it was because the volume can fluctuate with temperature, while the weight doesn’t.

Twin – Member
The point is, a given mass of fuel may have more or less volume depending on the temperature of the fuel as the fuel becomes less dense as it heats up. So if you fill up first thing in the morning when the fuel will be at its coolest, you will get more fuel (by weight) than if you filled up in the evening. Whereas if it was sold by weight, you would always get the same amount of fuel.

EDIT: too slow again!!

Fuel that is naturally a gas but sold as a liquid while constrained by a tank/bottle (petrol, liquid natural gas, Liquid petroleum gas) will always give an identical volume (KWh), temperature makes no difference. My LPG tank can only be filled to 85% in winter and 80% in the Summer, this is a safety requirement as an extreme temperature increase “could” course a blow out which would release liquid until the pressure drops. Propane in a bottle is sold by weight because it is easier for the multitude of sellers (re fillers of bottles) to work out how much they have put in. While LPG which is identical is sold by volume as it is delivered by tanker via a hose as in petrol. Butane is also sold by weight for the same reason as propane. Butane is the same as propane but does not have the chemical that stops it freezing ie it is only suitable for indoors (well at least during the winter). You have to remember that tank/bottle holds a liquid that turns to gas but as you remove the liquid the amount of gas increase to constrain the liquid there is no reason that temperature should make a difference as after all you have to chill it to turn it into a liquid in the first place……….now I am going back to my Sloe Cider so piss off!!!!

What about coke at McDonalds – 16oz. I thought ounce was a weight?

DrP

They are fluid ounces.

Racing at the TT [early 80s] we used to bring a freezer with us and plugged it in the garage of the B&B we stayed at and put the race fuel in it the night before, someone had bodged it to a certain temp that I don’t recall.

The fuel was then transported to the pits well insulated and put in the bike as late as possible, without freezing/cooling the fuel, we couldn’t reliably make the 2 laps we needed

They are fluid ounces.

Although, an [imperial] fluid ounce of water weighs an ounce 🙂

Although, an [imperial] fluid ounce of water weighs an ounce

Presumably at sea level, and 15C or 45F or whatever it is in those ancient measurements.

I believe aircraft measure fuel by weight.

Correct

The reason is because as stated above fuel density will change with heat

But the measurement becomes a bit more complex because as opposed to using a float with variable resistance the fuel capacity of the tanks is measured with capasitance values.

I remembers days working in C130 hercules aircraft fuel tanks sorting out fuel gauging issues orrable job

The question is prima facie quite logical since the calorific value is dependent on the mass not the volume. The volume will change by roughly 1% for every 10 deg C.

The reason we buy by volume is a simple case of its easy to measure accurately, and historically this is how it has been done. However I was told (by someone who worked for a petrol pump manufacturer) that actually the volumes are corrected for temperature – so you are buying “standard litres at 20 deg C” not a litre at the current temp.

Someone needs to re-sit basic organic chemistry. Butane is not the same as Propane, C3H8 versus C4H10. LPG is a mix of the two.

LPG is a mix of the two

Well the term LPG is a pretty general one without a strict definition and could be applied to pure propane, butane or any mixture of the two. There are a few other gases that it can also be applied to. Household or automotive LPG probably have a tighter specification but they are not the only specifications that exist.

However…

Butane is the same as propane but does not have the chemical that stops it freezing ie it is only suitable for indoors (well at least during the winter).

No, that’s wrong Butane just has a lower vapour pressure than Propane at a given temperature. There is no “chemical” that stops it freezing.

You have to remember that tank/bottle holds a liquid that turns to gas but as you remove the liquid the amount of gas increase to constrain the liquid

No, you remove the gas not the liquid and the liquid then boils to replace the gas, that’s why the take off is at the top of the tank. Well they are on Butane cylinders.

no reason that temperature should make a difference as after all you have to chill it to turn it into a liquid in the first place

Yes there is as in a storage situation both liquids are saturated therefore the ambient temperature dictates the pressure within the container. Also you can liquify both propane and butane by chilling it but you can also do it with pressure.

Oh and back to the OP the reason that we buy petrol by volume is because, as state earlier, it is easier to measure than mass.

Sandwich – Member
Someone needs to re-sit basic organic chemistry. Butane is not the same as Propane, C3H8 versus C4H10. LPG is a mix of the two.

Oooh bitchy bitchy. I noted my neighbours bottled gas now has the words propane AND LPG on it………Explain?

Cos it’s Liquified Petroleum Gas and it’s Propane. Propane being gas from petroleum.. no?

Can you name another example where a liquid is sold by weight rather than volume?

America.

Cougar – not really… a 16oz drink is 16 fluid ounces, which is a volume measure.

Butane is the same as propane but does not have the chemical that stops it freezing i.e. it is only suitable for indoors (well at least during the winter).

No, that’s wrong Butane just has a lower vapor pressure than Propane at a given temperature. There is no “chemical” that stops it freezing.
[/quote]
Explain the difference between propane and Butane as in where they both come from?

You have to remember that tank/bottle holds a liquid that turns to gas but as you remove the liquid the amount of gas increase to constrain the liquid

No, you remove the gas not the liquid and the liquid then boils to replace the gas, that’s why the take off is at the top of the tank. Well they are on Butane cylinders.
Opps obviously I meant remove the gas I have LPG central heating IE gas central heating. The LPG is delivered by tanker and driver puts it in my tank by pipe from the tanker and the price per liter is robbery!!!

no reason that temperature should make a difference as after all you have to chill it to turn it into a liquid in the first place

Yes there is as in a storage situation both liquids are saturated therefore the ambient temperature dictates the pressure within the container. Also you can liquefy both propane and butane by chilling it but you can also do it with pressure.
I am clearly talking about the amount put into my tank you are suggesting that if the tanker comes round on days when the temperature is different then I will get a different amount of LPG?? Please inform me therefore at what point do I gain in terms of KWh IE the colder outside the more I gain or the hotter? This would of course mean I would benefit if I left it latter in the year (colder) if that gives me a greater amount of LPG/KWh when I buy my LPG

Cougar – not really… a 16oz drink is 16 fluid ounces, which is a volume measure.

*nods* it’s derived from weight, though. In our case it’s the weight of water, and in the US it’s the weight of wine I think (I may be misremembering this).

But, yes, it’s a measurement of volume, despite the name. But that’s less amusing. (-:

at what point do I gain in terms of KWh IE the colder outside the more I gain or the hotter?

Is the tanker not temperature-controlled?

MidlandTrailquestsGraham – Member
LPG is sold by volume for vehicle use from a pump.
LPG (propane or butane) is sold by weight in cylinders.

Trying not to be pedantic MidlandTrailquestsGraham but not all of us on natural gas the nearest to me is over a mile away and it is a high pressure pipe. I have my LPG deliverd by tanker into a tank in the garden. Some people who use LPG in there cars also have tanks.

nods* it’s derived from weight, though. In our case it’s the weight of water, and in the US it’s the weight of wine I think (I may be misremembering this).

And ice cream and cooking oil and other liquids of various densities are still sold in fl. oz…

Less amusing? Can you be less amusing than not amusing at all? 😉

Explain the difference between propane and Butane as in where they both come from?

Propane is C3H8, i.e. it has three carbon atoms and eight hydrogen atoms.

Butane is C4H10, i.e. it has four carbon atoms and ten hydrogen atoms.

Because of this they have very different physical properties, however they are generally a product of refining crude oil.

I am clearly talking about the amount put into my tank you are suggesting that if the tanker comes round on days when the temperature is different then I will get a different amount of LPG??

In mass terms yes in volume terms no although the difference won’t be worth bothering about.

Please inform me therefore at what point do I gain in terms of KWh IE the colder outside the more I gain or the hotter? This would of course mean I would benefit if I left it latter in the year (colder) if that gives me a greater amount of LPG/KWh when I buy my LPG

No as I can’t be bothered, and I doubt you could afford my rates. It’d certainly cost you more than you would save. 😉

LPG – Propane/butane mix

LNG – Methane/ethane mix

TooTall – Member
Even in underground tanks you can have temperature variations that will change the volume of the liquid(s) present, so you should do the temperature calculations whenever you take a dip to ensure accuracy over the year

A dip??? Surely I cannot dip my LPG tank?
A/I would lose a lot of gas?
B/ It would be dangerous?
C/I don’t actually believe there anyway that a consumer could get into the tank?
There is a pressure gauge on the top which is supposed to tell me how much is in my tank in % terms. But they are reknowed for being highly in accurate most people who have LPG tanks according to the tanker drivers have a small rock on the top to “tap” the gauge so as to get a more accurate reading. Mine dropped about 10% once when I tapped it. Is that a product of tmpreture changes (sticky gauge). I am getting bored with this forum so other than an answer from

gonefishin

Please inform me therefore at what point do I gain in terms of KWh IE the colder outside the more I gain or the hotter? This would of course mean I would benefit if I left it latter in the year (colder) if that gives me a greater amount of LPG/KWh when I buy my LPG

No as I can’t be bothered, and I doubt you could afford my rates. It’d certainly cost you more than you would save.

The answer would involve saying cold weather is better than hot weather or vice versa……So I assume you don’t know the answer??

From a practical usage standpoint……

Butane & propane have very similar KWh. Either can be used to run a cookstove, heater, boiler, etc.

For *standard* residential & commercial usage, butane is no longer used and rarely available- propane is what is used in today’s marketplace.

The market shifted to propane because butane ceases to produce vapor (the stuff used in appliances) @ about 40 degrees F. This meant that the tank in most North American & European climates would either have to be buried OR have a pilot light under the tank to keep it warm :O)

Propane, on the other hand, continues to create vapor until about – 40 F making for a more stable & usable supply in a more economical aboveground installation, without the hazards of lighting a fire under it ;o)
Source(s):
20+ years in the propane industry

The answer would involve saying cold weather is better than hot weather or vice versa……So I assume you don’t know the answer??

Well you’re making the classic mistake of assuming that a simple answer requires little or no thought. What I would have to do is find what the actual composition of the LPG is, find out how the off loading systems work (e.g. is there any vapour recovery), find out if the tankers are refrigerated or not, and then use all that information to generate the data in question. This is something I can’t really be bothered doing espcially as the realtively small temperature changes we have in the UK will mean that the effect will be small, plus the fact that you are likely to buy your LPG “when you are about to run out” makes the whole exercise pointless.

No, you remove the gas not the liquid and the liquid then boils to replace the gas, that’s why the take off is at the top of the tank. Well they are on Butane cylinders.

Vehicle LPG systems with a built in tank use liquid withdrawal with a remote vapouriser.
Fork trucks use liquid withdrawal cylinders which lay on their side with an arrow to mark which way up they go so the pick up pipe is at the bottom.

Good point, SD-253, I was thinking of when I fill up my Land Rover from a pump. Of course, some people have got bulk tanks of their own for cars or heating.
How are they filled, by volume or weight ?