Question of the Day - Is Cold Gas Denser?
Question: Someone told me if I buy gas in the morning, when the gas is cold, will more gas fit in my tank and cost me less?
Answer: We keep getting this question and we believe the answer is no. First of all, gas is stored in underground tanks where the temperature will not vary much at all. Secondly, a cold liquid does not have a smaller volume than warmer liquid. However, if you buy gas in the morning, as you drive away from the pump, you might feel there is more power...
This has to do with the air temperature, not the gas. Colder air is denser, that's why they have intercoolers on turbochargers.
- Posted by
- Philip Reed July 7, 2006, 2:28 PM
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Sure the volume isn't going to change with temperature. A gallon is a gallon. But a liquids density does in fact change with temperature. For example, jet pilots always calculate their fuel requirements in pounds and must convert to gallons when ordering the fuel. When ordering a large amount, temperature is factored in when doing this conversion. A gallon of jet fuel at room temp weighs about 6.7 lbs/gal. Reduce the temperature and the weight will increase to 6.8 lbs/gal. Since an engine actually uses fuel by the pound, you'd get more with bang for your buck with colder fuel. This is a factor when you are ordering 50,000 lbs of fuel in a jet but I don't think it is worth the effort of even thinking about it when putting 100 lbs of fuel in your car. You might get an extra few ounces and save yourself a quarter.
http://www.omega.com/techref/flowmetertutorial.html
Scroll down to Part 3.2.
I want to thank drinkduff77 and carlisimo for excellent responses to my comments about filling your gas tank when it is cool. Since it appears that I was technically wrong that the volume of gas doesn't change, I'll do a follow up post about this. Thanks!