Chemistry Question : Ambient Air Temperature vs. Getting More Gasoline

[outrun]

Can any of the chemists here help to find a chart detailing Temperature vs Fuel Density.

My reasoning is this suppose the daytime texas summer temperature is 100F (37.78C) and add 17.3gal (65.49L) of Fuel. I could fuel up in the morning at a cooler 78F (21C).

The Fuel at this Temperature would be less dense than lets say an ambient air temperature of 11F
(12C) which we witnessed this morning in Delaware (cold!)

How many more pounds of fuel (or kg) am i getting if i fuel up right now assuming the same metering of 17.3gal. I know aircraft go by pounds of fuel.


I am trying to get more fuel for the money therefore if someone can find me a Fuel density chart or equation I would appreciate it. (Unless the gains are negligible)

Thanks-

 

[Shannow]

The fuel companies down under are using this phenomenon to great effect.

They're selling the fuel per litre at high temperature from the back of the tanker, in summer heat.

The station stores it underground at around 15-20 degrees celsius, which is a fairly constant temperature regardless of the time of day and season. The fuel contracts, and they can sell less litres than they paid for.

So the fuel companies win by a significant margin.

Your problem is that once it's underground for a bit, the density is constant.

 

[TheTanSedan]

As a Dallasite, I fill in the very early morning in summer. BUT (and it is a big but) only if I am going to immediately drive off some of that fuel. The gasoline re-expands and puts significant pressure on the tanks ability to maintain equilibrium vis-a-vis emissions and other ventilation equipment. Fuel level should be down from the extra-full mark for best long-term results.

Re-formulated gas is a bigger "problem", IMO, and I just add it all to the cost of ownership/operation.

 

[mph]

Assuming that your strategy is to refuel when it's cold (e.g. just before sunrise) rather than to actually travel hundreds of miles to a more northern clime, you'll find that since the fuel is stored underground, its temperature is much more stable than the outside air.

Anyway, this comes up with some frequency on Usenet and the consensus is that it's pointless. Try searching groups.google.com.

 

[Ken4]

My understanding is that those underground tanks are enveloped in water.

 

[Shannow]

Ken,
at least down here, they are buried in sand.

If the water table is high, then there will be a water level outside the tank, but that's undesirable. (potential flotation)

 

[MolaKule]

The density of most fluids decreases with increasing temperature.

For the mass, volume, and density, the equation is: (at 1 atmosphere or 14.7 psi)

m = rho.V, where the mass is in kilograms [slugs], rho is the density (kg/m^3)[slugs/ft.^3], and Volume is in m^3[ft.^3).

Gasoline has a density of 745 kg/m^3 at 20 C and drops only about 4.7% at 100 C.

Edit: Found a better table; (University of Wisconson, Madison)

C Density

40 738
50 733
60 728
70 724
80 719
90 715
100 710
110 706


Hope this helps.

[ January 25, 2003, 12:29 AM: Message edited by: MolaKule ]