One strategy, if you are going to the beach (east coast beach such as Ocean City Maryland) is not to go on a full tank. For some reason gas is ~ .20 to .60 cheaper on the coast. My car can get there with the tank only half full. Then I fill up before heading home.
IMO this is one reason I should go to the beach more often 
Depends on where you are. At our beach areas prices are higher than farther inland.
A large chunk of the retail price of gasoline is state taxes. If you live in a state with high taxes near the border with a state with low taxes there can be a significant difference. Folks near Maryland may live in small enough states that lots of them are near borders and could do the tax arbitrage. It’s an 8 hour drive to the nearest state border for me.
Not only that, but the vast majority of drivers have to fill up far too regularly to take advantage of changing prices with anything like the level of savings asserted by Melbourne in his/her post.
For example, i have a car that gets over 32 miles to the gallon in all driving, and i still fill up about three times a month. Using your chart, the most i could possibly have saved on a 10-gallon fill by waiting for a price drop, without actually running out of gas, would have been maybe 5c per gallon, or about 50c per top-up.
Melbourne seems to be suggesting that, with some canny timing, you can save $5-7 per fill-up on a regular basis. That does not seem possible to me.
I just buy gas when I need it and don’t worry. I’m sure I’m doing just fine - call it “dollar cost averaging.”
I fill up once a week. Our present price cycle is about 12c per litre, over about a month. Our present cycle has a sharp rise, a slow decline (about 1c per day) then a long flat bottom (around 2 weeks). I won’t buy a full tank at the peak, or immediately after the peak. Instead, I let it get very low, then just put in $20.
When I was young, and there was a variable cycle over around 10 days, and the motor-cycle only had a small tank, I just filled up whenever, but I kept a record of the price, which allerted me to the fact that there was price cycle. Some people, like my wife, never realised that there was a discernable price cycle.
When we had the fixed weekly cycle, I always filled up Tuesday night. Since my wife did not realize that there was a price cycle, she always filled up Sunday afternoon. Not at the exact peak (Monday), but ~ 25c /American gallon more than the Tuesday evening price.
A 12c per liter fluctuation over a month equates to about 46c per US gallon, which is far larger than the typical changes in the US, or at least where i live in Southern California. With those sorts of swings, i could imagine saving some real money through judicious timing.
And, in my neighborhood at least, there does not appear to be any of the within-week fluctuations that you describe here (e.g., Tuesday v. Sunday). I see the gas price at my local station virtually every single day, because i have to drive by it almost no matter where i’m going (work, gym, supermarket, etc.), and i keep a close eye on prices. We get none of this sort of flip-flopping. Our gas price took a 10c/gallon drop last week, but that was part of a medium-run trend (ik.e., the last couple of months), and it’s remained at the lower price without change for five or six days now.
Edit: I’d be interested to know if any other US folks see the sort of short-run peaks and troughs that Melbourne describes.
I don’t, at least not on a weekly basis. The prices do sort of rise and fall, but not very predictably- if you look at the chart I posted up thread, there are monthly peaks and valleys, but they’re at any point during the month, so there’s no good way to know where you are in the cycle, and if there are oil price changes going on, that obfuscates that cycle almost entirely anyway.
I just try and get the cheapest gas that I can at any given fillup (without driving an inordinate distance to do so)
Yeah, I was going to say: if you find a method that works, PM me! And please keep it a secret, otherwise!
But there may be special attributes to the gas situation that make it different. So far, I don’t see any, unless there is a weekly cycle. As noted above, I’d think that if there was a significant weekly cycle, people would take advantage of it to the point that it would diminish to insignificance, thanks to normal market pressures. On the other hand, if enough people don’t sweat the pennies, there may not be a strong enough force.
Something I keep in mind as I fill my nearly 20 gallon tank (usually when I’m on fumes), is that a 5 cent discount saves me $1 out of nearly $70, less than 2% savings, so I don’t sweat it.
The drain is always well above the bottom of the tank. For example, my car has a 20 gallon tank, which runs out of gas after using 19 gallons, according to the literature. I haven’t tried to verify this.
You’re “not even wrong.” How do you detect a peak? It’s surprisingly difficult to do, until it’s far too late, just as with the stock market.
(I have a little related hobby experience, writing script code to detect aspects of audio files to build “soundfonts”, and while I didn’t do a serious research into the topic, it was surprisingly more difficult to do than you might guess, without either processing the whole sample or using rather arbitrary heuristics.)
Now, if you say something like, “fill up whenever the price drops by X cents from the day before and you have at least Y gallons to buy”, that would be a testable hypothesis, and we could even run the algorithm against historical data to see if it holds up (if someone can find good historical data in a form that’s easy to export.)
Here’s a twist to the question at hand. Is it cheaper in the long run to buy 100% gasoline at a higher pump price (.40 per gallon) than buying 10% ethanol blended gasoline? I Purchased the 100% gasoline last week and got a better than two miles per gallon. For $10 extra i seen alittle over 50 more miles on that tank of gasoline.
I think you can do arbitrage to a certain extent. If driving home you hear on the radio that oils prices have spiked, it might make sense to fill up before the price increase hits at the pump. And if they have just dropped it might make sense to wait a few days until the decrease hits. But your tank has to be at the right level and the increase or decrease has to be significant to save any real money.
Figure it out for yourself. How much do you pay for each type of fuel i.e. what is the per gallon? How many miles per gallon do you get with each fuel? Divide the two numbers for each case. That is, per gallon divided by miles per gallon gives you per mile. Whichever fuel gives you the lower per mile is better.
I’d be happy to do the math for you, but you didn’t include all 4 numbers we need.
Our Prices are somewhat predictable with hikes of about 20 cents every week or so. You aren’t always going to hit the bottom exactly, but when it’s down about 15 cents from the last peak you better be thinking about buying. It can save you a couple of dollars a week which is a hundred or so per year.
As I’ve discussed above, I have clear peaks in my gas price cycle. It’s not like our stockmarket or currency markets. My gas/petrol market has been driven by intense competition, and structural factors like weekly delivery and, (as discussed above) the effect of the supermarket coupon discount scheme.
I put a fair amount of random thought (while driving home) into the optimum strategy for buying when you had a limited number supermarket coupons, so when this topic came up I immediately jumped to the assumption that you had a similar market.
However, my personal experience is that not everyone notices prices cycles, so I also wouldn’t assume that you are correct in suggesting that you don’t have clear peaks in your gas prices.
Would it be worth buying a more economical car when you next visit the dealer?
I’m sure the savings calculations would be easy.