# Practical petrol ponderation

sonhouse
Posers and Puzzles 25 Sep '06 03:08
1. sonhouse
Fast and Curious
25 Sep '06 03:08
You see the price of petrol going down but its still very differant from place to place. You know about a gas station that has gas cheaper than the one a couple of blocks from home. So make a formula that takes into account the money you save by going to a distant gas station vs. the distance. Obviously if you drive 50 Km to save a couple of pennies per liter you probably spend more for the trip than the savings. So what is the formula for figuring out all such cases?
2. PBE6
Bananarama
25 Sep '06 04:07
Originally posted by sonhouse
You see the price of petrol going down but its still very differant from place to place. You know about a gas station that has gas cheaper than the one a couple of blocks from home. So make a formula that takes into account the money you save by going to a distant gas station vs. the distance. Obviously if you drive 50 Km to save a couple of pennies per lit ...[text shortened]... pend more for the trip than the savings. So what is the formula for figuring out all such cases?
Let:

S = savings (dollars)
B = base price of petrol (dollars/litre)
C = cheaper price of petrol (dollars/litre)
V = volume of petrol purchased (litres)
d = distance between petrol stations (kilometers)
k = mileage proportionality constant (depends on average speed, car design, car condition, etc...) (kilometers/litre)

Assuming you will do either of the following:

(a) drive an insignificant distance to the base petrol station, purchase enough petrol to completely fill the tank, then drive an insignificant distance home; or

(b) drive some distance "d" to the cheaper petrol station, fill up enough petrol to completely fill the tank, plus purchase enough petrol in a can so that you can fill up the tank completely when you get home, then drive home (same as driving to the base petrol station) and fill up the tank;

Then:

S = B*V - C*(V+2*d/k)

The break-even point occurs when S=0, which gives:

B*V = C*(V+2*d/k)

C = B*V/(V+2*d/k)

Here are some typical values for me:

B = 0.85 dollars/litre
V = 40 L
d = 5 km
k = 9.8 km/L (2002 Ford Taurus)

With these numbers, the break even cheaper price would have to be 0.828 dollar/litre before I would start saving money. But even if the cheaper price were 0.80 dollars/litre, I'd only be saving about \$1.18 on a \$34 purchase. Probably not worth the hassle of the extra drive and putting in more petrol from a can.
3. uzless
The So Fist
25 Sep '06 14:151 edit
Originally posted by PBE6
Let:

S = savings (dollars)
B = base price of petrol (dollars/litre)
C = cheaper price of petrol (dollars/litre)
V = volume of petrol purchased (litres)
d = distance between petrol stations (kilometers)
k = mileage proportionality constant (depends on average speed, car design, car condition, etc...) (kilometers/litre)

Assuming you will do either of ase. Probably not worth the hassle of the extra drive and putting in more petrol from a can.
plus wear and tear on your vehicle driving the extra distance...and I think there should be a "danger" variable proportional to the distance driven...might get in an accident which would shoot your costs way up.

Then there's also the fact the road will get worn out a bit quicker by you driving your 2 tonne car down it, which means the city will have to pay to repair it that much quicker, which means your taxes will have to be raised to pay for the road repair.

The stress you may incur from the extra drive may impact your health and cause you to go see the doctor which may or may not cost you money depending on if you have health insurance and what the deductible is.

And if you had to call the wife to tell her you'd be late for dinner because you are driving further away for gas will probobly cost you 10cents/minute on long distance charges.
4. sonhouse
Fast and Curious
29 Sep '06 18:262 edits
Originally posted by uzless
plus wear and tear on your vehicle driving the extra distance...and I think there should be a "danger" variable proportional to the distance driven...might get in an accident which would shoot your costs way up.

Then there's also the fact the road will get worn out a bit quicker by you driving your 2 tonne car down it, which means the city will have to pay driving further away for gas will probobly cost you 10cents/minute on long distance charges.
So the gist of that is: Ride a bicycle! maybe with a solar powered electric motorðŸ™‚
The solar panels could be over your head and thus protect you from the flaming sun and give protection from rain. Of course it a big wind comes up, you are in trouble.....
The car in PBE6's example in US stuff is this: gets 23 MPG, gas costs \$2.90 per gallon(US) and he drove only about 3 1/8 miles and the price would have to drop about 11 cents per gallon US to be worth the effort to drive. I am suprised by the amount it needs to drop to be worthwhile, especially because the distance is so short. Of course the actual miles driven is twice so its a round trip of 6 1/4 miles to save the money. Interesting, no?
5. 30 Sep '06 03:52
Originally posted by sonhouse
You see the price of petrol going down but its still very differant from place to place. You know about a gas station that has gas cheaper than the one a couple of blocks from home. So make a formula that takes into account the money you save by going to a distant gas station vs. the distance. Obviously if you drive 50 Km to save a couple of pennies per lit ...[text shortened]... pend more for the trip than the savings. So what is the formula for figuring out all such cases?
i believe the word is gasoline, not petrol
6. sonhouse
Fast and Curious
30 Sep '06 16:39
Originally posted by TDR1
i believe the word is gasoline, not petrol
I was telling the Eurotrash versionðŸ™‚
7. 30 Sep '06 17:12
That's why I love so much my bicycle ðŸ˜›
8. sonhouse
Fast and Curious
30 Sep '06 17:41
Originally posted by CrazyLilTing
That's why I love so much my bicycle ðŸ˜›
Indeed. It's the most efficient people transport known to mankind.
9. 01 Oct '06 06:18
Yeah... walking is so less efficient, with all that requirement for extra equipment and refinement of materials. Good point.
10. 03 Oct '06 06:111 edit
Originally posted by TDR1
i believe the word is gasoline, not petrol
And you call it "gas" because it's a liquid?

What's the US for "Liquid Petroleum Gas" ?
11. sonhouse
Fast and Curious
03 Oct '06 16:01
Originally posted by aging blitzer
And you call it "gas" because it's a liquid?

What's the US for "Liquid Petroleum Gas" ?
Propane
12. sonhouse
Fast and Curious
03 Oct '06 16:03
Originally posted by Gastel
Yeah... walking is so less efficient, with all that requirement for extra equipment and refinement of materials. Good point.
Ok, lets see, anyone know the differance between the environmental impact for making shoes v bicycles?
13. uzless
The So Fist
03 Oct '06 19:04
Originally posted by aging blitzer
[b]And you call it "gas" because it's a liquid?

[b]
No it's gasoline...gas for short. Ever heard of homonym?
14. 04 Oct '06 02:18
Originally posted by sonhouse
Ok, lets see, anyone know the differance between the environmental impact for making shoes v bicycles?
You need shoes to walk? Hmmm.... thank goodness Nike was the first corporation ever! All those mammoths would have been impossible to overcome without the Nike 'Game Stalker' (Jordan edition).
15. 04 Oct '06 07:32
Originally posted by uzless
No it's gasoline...gas for short. Ever heard of homonym?
That would make it an abbreviation.