Fuelly Forums - expanding gas and fillups

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Only if you get your gas from a station that stores it in refrigerated plastic bottles at night, then puts 'em in the sun once it rises. ;) I mean, .2% can make a difference, but there are a ton of things to do that'll show much larger gains.

Quote:

Originally Posted by Cummins

Rock-Solid Rules
§ Every 2% reduction in aerodynamic drag results in approximately 1% improvement in fuel economy.
§ Above 55 mph, each 1 mph increase in vehicle speed decreases fuel economy by 0.1 mpg.
§ Worn tires provide better fuel economy than new tires, up to 7% better fuel economy.
§ Used lug drive tires can get up to 0.4 mpg better than new lug tires.
§ Ribbed tires on the drive axles provide 2–4% better fuel economy than lugged tires.
§ Every 10 psi that a tire is underinflated reduces fuel economy by 1%.
§ The break-in period for tires is between 35,000 and 50,000 miles.
§ Tires make biggest difference in mpg below around 50 mph; aerodynamics is the most important factor over around 50 mph.
§ The most efficient drivers get about 30% better fuel economy than the least efficient drivers.
§ Idle time is costly. Every hour of idle time in a long-haul operation can decrease fuel efficiency by 1%.

What the hell are you rambling about? Pump it in a plastic bottle...

Yer analogy. Putting it in the fridge, then the sun, is going to show a much larger difference than the driver will see at the gas station when filling in the morning compared to afternoon, unless the gas station stores their gas in the same way. :p I suppose you could measure the volume, put it in the fridge for a few minutes until it drops a few degrees, which is the difference you'll see at the station, then measure it again, but I don't think most people have accurate enough equipment to measure a .00095% difference in volume per degree C.

BUT, the temperature change will also make your bottle shrink or expand. Plus, just on general principles, I don't want any of my pals putting gas in soda bottles.

In soda bottles or in the fridge either. I think you would need to take a gallon gas tank and fill it at different times to see the difference if any. Good luck on the research project.

Arrrrr, you guys take everything too literal and straightforward :P.

I was just offering an example how to measure the gas fluxuations. I wasnt saying that the gas actually changes that much, I was just proposing an way to see the drastic changes and how temperature CAN effect expansion..

If you leave the cap loose, the bottle wont change..

And perhaps we are looking at this differently. Seems I am looking at it like "how much the gas station saves by a small variable" as everyone else is thinking "how much I save"....I have a 8 gallon tank, so equals next to nothing..gas stations have 10,000 gallon tanks..

Quote:

Originally Posted by baddog671 (Post 70428)

If you leave the cap loose, the bottle wont change..

For a homogeneous plastic, such as PET soda bottles, thermal expansion will occur evenly and uniformly in all directions, assuming an even material temperature change. The bottle will still expand/contract with a loose cap.

Quote:

And perhaps we are looking at this differently. Seems I am looking at it like "how much the gas station saves by a small variable" as everyone else is thinking "how much I save"....I have a 8 gallon tank, so equals next to nothing..gas stations have 10,000 gallon tanks..

Fair enough :) For a 10,000 gallon tank - each 1.8F will change the volume by 9.5 gallons. On a small scale (2L bottle - even a 10 gallon fuel tank), very few (if any) of us have access to measure that volumetric change with the resolution, precision and accuracy to be valid....

Quote:

Arrrrr, you guys take everything too literal and straightforward :P.

Yeah, it's not as bad as academia though. Literal, with log books for confirmation :p

Have you ever seen a sealed gas jug expand? In the afternoon itll look like its about to bust and in the night itll look like someone crushed it like a coke can. Your saying a plastic bottle wont do the same as a platic jug?

The experimentation has already been done. The ASTM has published tables to correct for the thermal expansion of all types of hydrocarbons. There not all the same and also not linear.
If I remember I'll look up the correction factors that apply to gasoline when I get back to work next week and list a few that cover ambient temps.

Ok I finally got round to looking up the correction factors today. The volume correction factors are taken from the ASTM book "Petroleum Measurement Tables Volume Correction Factors Volume II Table 6B".

The table requires you to know the API gravity, so I used 60API which is about an average value for gasoline.

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