I herd that you should buy gasoline during coolest time of day - early morning or late evening being best and that during these times gasoline is densest. Gas pumps measure volumes of gasoline, not densities of fuel concentration and you are charged according to "volume of measurement". Is this true?

From 50 ways to save on gas (WNBC):

quote:

18. Fill up when cool
Early morning or late evening. Cooler temperatures mean less vapor.

“From the environmental standpoint, it's better to fill up your tank in the cooler hours of the morning or the evening,” said Ray Werner, Chief of the Air Programs Group in New York, Environmental Protection Agency. “Gas is less volatile and won't evaporate quite so quickly and form ozone damage in the environment. So we recommend early morning or late evening.”

...so according to them it's really about minimizing evaporation at the nozzle -- not maximizing density of liquid. California was one of the first states to mandate those accordion boots around the filling nozzle, which recover otherwise lost vapor (that you've paid for!). If you fill up in the daytime, pick a pump in the shade.

On the other hand (from OilWatchdog.org March 2007):

quote:

When the temperature of gasoline rises above 60 degrees, gasoline expands but California pumps don't account for the bigger volume and consumers receive less gasoline than they should.
...
Reporter Steve Everly found fuel pumps that do not adjust for temperature cost Californians at least 3 cents for every gallon in warmer weather, approximately $500 million in industry profits per year, and overcharge Americans more than $2.3 billion annually.

Three cents a gallon represents around a 1% decrease in density for gasoline "in warmer weather." How I wish the biggest concern over the price of gasoline was a 1% pump error.

I'm surprised that ambient temperature is relevant here, because the supply tanks are deep underground, where the temp should be fairly constant. Evidently if its blazingly hot at the surface, the gasoline has time to warm up enough before entering the volume meter inside the pump -- boosting the price a little more. Now if I could just figure out how to cool off my wallet at the pump...

The plot thickens. This is from a June 2007 report of a House subcommittee chaired by Dennis Kucinich:

quote:

Findings:
• The oil industry has known for 100 years that gasoline expands with temperature. As it warms, gasoline expands by volume but not by weight or energy content. Since the 1920’s, the oil industry has taken temperature into account for wholesale transactions, and use a 60 degree Fahrenheit standard when measuring gasoline at wholesale. But the oil industry does not adjust for temperature in retail sales to consumers. As a result, consumers pay a Hot Fuel Premium when gasoline temperatures exceed 60 degrees, as they do during the summer.
• 513.8 million gallons of gasoline sold in the summer 2007 will be attributable to the thermal expansion of gasoline.
• Consumers will pay a hot fuel premium of about $1.5 billion in the summer 2007.

So when it comes to saving money on gas and getting the most out of your dollar, a yay or nay on this theroy?

Since my per/capita share of those expansion gallons appears to be 1.71 gallons per year; assuming that Dennis Kucinic's comittee is right and I buy all my gas during the heat of the day, I might save as much as 1.71*4.00=$6.84/year by buying my gas at dawn every time, and live in Green Bay or Alaska. Yay or Nay depends on how frugal one is, IMO.

Blimey, what a country of misers and tightwads ! Never heard of that. We pay, according to an American news report, $9-80 a US gallon, but never worry about the fuel temperature.Of course, we don't get some American temperatures We have a Goldilocks temperature most of the year, with no excitement unless the mercury hits the equivalent of 85F ! In our case, extra evaporation is not going to concern us much

Apart from that , we save fuel by driving diesel engined cars. Tests of a diesel BMW, max speed 140 mph, showed a better fuel economy than a Toyota Prius hybrid. We know which we prefer .

Fred - Is diesel fuel less expensive than regular gasoline there? I know for my area, diesel is even HIGHER than premium gasoline!

I doubt that I'll ever buy another new car, but if I did, I would be buying electric. For now, I'll be happy with my Toyota Corolla, which gets upwards of about 35 mpg...it STILL hurts at the pump though!

Giz, while the price of diesel is higher, you can get more mile per DOLLAR on diesel fuel.

Diesel engines get more miles per gallon of diesel then regular car engines on regular gas.

Therefore it is cheap to drive a diesel.

Now what gets me, the fact that diesel fuel requires less refining then gas and should be cheaper. I think the extra cost comes making diesel fuel meet EPA rules for emissions.

I don't care how many miles I get per gallon. I want to know how many miles I get per dollar. Sometimes you can save money simply by change grades of gas. You may pay a few more cents per gallon for a higher grade and find that you get more mile per dollar on that higher grade.

Gizmogram,in Britain the price difference is small. A litre of unleaded is about 107 pence and a litre of diesel is about 114 pence. Modern European diesel cars have low emissions and do a great many more miles to the euro or pound than the identical 'petrol'[gasoline] car.

Whilst the modern diesel would pass US laws on emissions and drives like its rival, it is hard to persuade an American that a diesel is anything other than a truck engine . Meanwhile every one of the luxury car makers, with the exception of Rolls Royce and makers of fast high-performance cars such as Aston Martin, makes a diesel version alongside the petrol one. Our executives happily drive a diesel Jaguar, Lexus or BMW

In Western Europe, most new cars are diesels and hire cars almost invariably are: the rental companies only have petrol cars by default. One consequence is that Avis and Hertz have to stick very clear warnings on their cars here, lest visiting Americans refill them with petrol and not diesel

Further to the above:

A letter writer to The Times today (Good Friday) says that a) a diesel vehicle uses 30 per cent less fuel than a petrol vehicle b) all diesel now sold contains an element of biofuel, which fact should appeal to those of a 'green' persuasion.

The economies are , therefore, substantial.

In a part of the world where fuel costs so much (entirely because of the high taxation on fuel) fuel economy is highly desirable if the performance of the vehicle is unaffected (as, indeed, is the case now)

Incidentally, there has been some talk of raising the tax on fuel in the US. A figure of 50 cents a gallon has been suggested. That won't work to reduce consumption. The increase would need to be of a 'draconian' level before it had any noticeable effect.Americans don't seem to have any ready alternative to the car,nor any incentive to avoid use of one,it remaining an essential to life there. Only 6 per cent of American workers go to work by public transport. Americans have an enormous rail network but they don't use trains.The average Swiss travels 2,040 kilometres a year by train.[A kilometre is 5/8 of a mile] The Japanese travels 1,922, the French 1,284, the Briton 734 (Britain's a small place, but we do our best. I'd not think to take the car anywhere served by a direct rail line ) Can't find a figure for the American: the US doesn't appear on any chart I can find!

quote:

Americans don't seem to have any ready alternative to the car,nor any incentive to avoid use of one,it remaining an essential to life there.

I think public transport is pretty good in North America between major urban centres, but not so impressive in connecting people in small towns with each other, or getting them into the big cities. You are right; there just isn't any incentive to stop using cars.
The smallest villages in the UK have some type of bus service, but that isn't the case here.
I live in a town of about 3,500 people. It's about 20 minutes drive from the city. We have no public transport here. Everyone depends on cars, and I think this sort of situation is fairly common in small towns in North America.
Yes I agree, there would have to be extreme measures taken before people, who do have access to rail, or other forms of transport, stopped using their cars. However, I think price increases might affect the sales of SUV's. We are already seeing an increase in the sales of compact cars here.