What does fuel weigh?

Submitted: Friday, Mar 31, 2006 at 19:29
ThreadID: 32391 Views:14514 Replies:5 FollowUps:15
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I'm trying to calculate some load bearing and carrying capacities. I know petrol/diesel/oil all weigh less then water. I've generally just calculated petrol at a kg per litre (as per water) as a rule of thumb. I know it's less than that, but exactly what does it weigh?

Any Scientists out there?

Cheers,

Jim.
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Reply By: Member - Blue (VIC) - Friday, Mar 31, 2006 at 19:36

Friday, Mar 31, 2006 at 19:36
I think the specific gravity of unleaded is .81 Not sure about diesel or oil.
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Follow Up By: Member - Blue (VIC) - Friday, Mar 31, 2006 at 19:45

Friday, Mar 31, 2006 at 19:45
OK, let me give you what the good chart here at work tells me...

Oil, mineral, automotive engine: .83 - .86/ will depend on additives

Diesel automotive: .82 - .95 depending on level of refinement and additives

Petroleum, unleaded automotive : .74
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Follow Up By: Exploder - Friday, Mar 31, 2006 at 19:58

Friday, Mar 31, 2006 at 19:58
And that’s why Aeroplanes order fuel to weight and not litres also why they try to get it when it’s cold.

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Follow Up By: Member - John R (NSW) - Friday, Mar 31, 2006 at 20:30

Friday, Mar 31, 2006 at 20:30
Diesel's close to Jet A. We load it at .768kg/L

Exploder, we order fuel in pounds (set the fuel bugs on the refuel/defuel panel, calibrated in pounds).

The refueller charges us in litres.

The Load Controller enters it on the trim sheet in Kilos.

So we have to do 3-way conversions most of the time. I've never used temperature as a reason for buying fuel however. I use location (price) and weight limitations as my guide. :-) Sydney's generally cheaper than Coffs or Canberra for Jet A.
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Follow Up By: The Explorer - Friday, Mar 31, 2006 at 21:00

Friday, Mar 31, 2006 at 21:00
Exploder posted this followup
snip".. also why they try to get it when it’s cold. "

Would be interested to know how "they"(?) "try" and do this..please elaborate.

Cheers
Greg
I sent one final shout after him to stick to the track, to which he replied “All right,” That was the last ever seen of Gibson - E Giles 23 April 1874

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Follow Up By: Exploder - Friday, Mar 31, 2006 at 22:06

Friday, Mar 31, 2006 at 22:06
Like the Flyboy said above he’s never done it, I just remembered when I studied aviation when I first left school, one of the lecture's made a mention of this, can’t remember much of any of it now but when I read this “735kg / m3 at 15 deg C” below it just jogged the memory a bit.

Like the above post said it’s measured in Weight/ pounds and that’s some how because of America apparently.

I remember doing those fuel and loading cacations for the 727.

Still got the Jefferson Flight computer or Wiz wheel somewhere, also know as the prayer wheel as you prayed to god that you used the thing right LOL. Along with a hole heap of text book’s.
.
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Follow Up By: The Explorer - Friday, Mar 31, 2006 at 22:28

Friday, Mar 31, 2006 at 22:28
..Further to my last post regarding comment on "why they try to get it when it’s cold"...it actually wouldnt matter. If you are purchasing fuel by weight then temparature is irrevalent...only the volume changes i.e. cold or hot you will get the same amount (number of atoms - mass) of fuel if weighed. eg order 3000 kg of fuel and you will get 3000 kg of fuel what ever temperature is. Its only when paying by volume does temperature become an issue as volume will be greater at higher temps for same amount of actual (atomic mass) of fuel.
Cheers
Greg
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Follow Up By: Member - John R (NSW) - Saturday, Apr 01, 2006 at 07:42

Saturday, Apr 01, 2006 at 07:42
Bwahahaha! The old 727 (80 ton Dog Whistle). Jeez I pulled some hair out doing One engine inop and depressurised PNR's. Fortunately it grew back.

Nowadays the most complex daily calcs we do is the 3 way conversions I described above.

SG 0.8 is close enough I reckon.
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Follow Up By: howie - Saturday, Apr 01, 2006 at 20:27

Saturday, Apr 01, 2006 at 20:27
i think 15 deg C is the temp at mean sea level for a 'standard atmosphere'.
so i tried to think but cannot remember them weighing buckets of fuel on a bathroom scale on the tamac when filling a jumbo up.
they must use some sort of conversion chart for temp/litres, which would be quite useful when filling up with 20,000L.
20,000L @ 15 deg C = 20,000L
20,000L @ 25 deg C = ?
last words on the cockpit recorder " i say captain, did you check the ground temp"
"no, i thought you diiiiiiiiiiiiiiiiiiiiiiiiiddddddddddddddddddddddd................"splash.
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Reply By: Member - Stillthinkinaboutit - Friday, Mar 31, 2006 at 19:46

Friday, Mar 31, 2006 at 19:46
The MSDS for BP Regular unleaded states :

735kg / m3 at 15 deg C

So that means 0.735kg / L

Regards,
Mark
AnswerID: 164140

Follow Up By: Lone Wolf - Friday, Mar 31, 2006 at 19:52

Friday, Mar 31, 2006 at 19:52
Now, your average Mars Bar, on the other hand, weighs in at around.......

Sorry Jim, couldn't resist.

Wolfie
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Reply By: hopscotch - Friday, Mar 31, 2006 at 19:59

Friday, Mar 31, 2006 at 19:59
Rule of thumb:-

Petrol .735 to .775 kg per litre

Distillate ADO or diesel -( all the same thing) .835 to .850 kg per litre.

It varies a little from refinery to refinery depending on the original crude and the particular refinery equipment but the difference in load is akin to whether you have had your lunch or not.

Makes a difference to trucks carrying 1500 litres.

Kevin J
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Follow Up By: Jimbo - Friday, Mar 31, 2006 at 20:02

Friday, Mar 31, 2006 at 20:02
Thanks Kev
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Reply By: Jimbo - Friday, Mar 31, 2006 at 20:01

Friday, Mar 31, 2006 at 20:01
Blue/Mark,

Scholars, the pair of you. I never thought petrol was quite that light. Live and learn eh?

Ian,

Your wit certainly exceeds your looks (so does your ar$e, LOL). You're one quick prick with a selective memory. As always, you keep us all entertained.

Cheers,

Jim.
AnswerID: 164145

Follow Up By: Warrie - Friday, Mar 31, 2006 at 20:51

Friday, Mar 31, 2006 at 20:51
Fill up your 20 litre plastic jerry can with water and then another with petrol. Carry both at the same time to your bathroom scales by which time you'll have noticed the considerably different weights. Ignoring the plastic you should read 20kg for the water and 14kg for the petrol. PS LPG is about 500grams per litre. Cheers.
Warrie

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Follow Up By: Member - Blue (VIC) - Friday, Mar 31, 2006 at 21:27

Friday, Mar 31, 2006 at 21:27
I can read an SG chart Jim, I still can't work out bloody electronics though... But I must be doing something right, my car still moves forward and my beer is cold.
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Follow Up By: Michael ( Moss Vale NSW) - Friday, Mar 31, 2006 at 22:02

Friday, Mar 31, 2006 at 22:02
Warrie!! bathroom scales are not accurate, every time i get on them, the reading is higher!! What gives? :)
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Follow Up By: Exploder - Friday, Mar 31, 2006 at 22:08

Friday, Mar 31, 2006 at 22:08
To many mars bars
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Follow Up By: GaryInOz (Vic) - Saturday, Apr 01, 2006 at 10:43

Saturday, Apr 01, 2006 at 10:43
Michael (Moss Vale NSW)

to bastardise a legal term, they are the "Scales of Injustice".
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Reply By: Kiwi Kia - Saturday, Apr 01, 2006 at 10:26

Saturday, Apr 01, 2006 at 10:26
You have had the answers but here is another angle if it is any easier;

Petrol = 72% wt of water

Oil (engine) = 90% wt of water

So, if you are a grey nomad and know the capacity of your tank in gallons but do not yet get the hang of conversions to metrics :-)) you can now sort things out in your mind for what the relative weights are.
AnswerID: 164228

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