City-Data Forum What is the equation for calculating gas price between two cars? (vehicle, fuel)
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02-13-2019, 12:50 PM
 28 posts, read 8,467 times Reputation: 33

There are many calculators online but all assumes that the gas price will be the same for the two cars.
In the case that one car uses premium gas, what would be the equation to calculate the difference in monthly gas cost for two cars?

02-13-2019, 12:53 PM
 6,982 posts, read 4,038,554 times Reputation: 9340
...gallons used * price of gas for both, subtract difference.

02-13-2019, 12:54 PM
 Location: Aurora Denveralis 7,659 posts, read 2,685,014 times Reputation: 11640
(Gallon Price A) * (MPG A)
-----------------------------
(Gallon Price B) * (MPG B)

...yields the per-gallon mileage cost difference ratio between the two cars. Other very simple kitchen math will generate other related numbers.

02-13-2019, 12:54 PM
 Location: Los Angeles 12,075 posts, read 10,173,177 times Reputation: 32728
What premium typically costs in your area times amount of gallons you purchase per month minus what you pay now. That's the increase.

02-13-2019, 12:56 PM
 Location: BFE 1,271 posts, read 398,326 times Reputation: 3857
Ain't Math Magical?

02-13-2019, 02:16 PM
 Location: Aurora Denveralis 7,659 posts, read 2,685,014 times Reputation: 11640
Quote:
 Originally Posted by Gatopescado Ain't Math Magical?
Do you have an online calculator that proves that?

02-13-2019, 04:00 PM
 Location: BFE 1,271 posts, read 398,326 times Reputation: 3857
This is as close as I got: https://www.youtube.com/watch?v=LVfe6rdHRKI

02-13-2019, 07:00 PM
 1,180 posts, read 418,844 times Reputation: 3597
Don't use MPG to compare.
Use MP\$.

02-13-2019, 07:42 PM
 Location: Raleigh, NC 2,156 posts, read 3,320,471 times Reputation: 2693
Keep in mind that "Premium" gas isn't named that way because it is "better" or automatically gets you higher mileage.
It just means it has a higher Octane Number. Which is an additive that lets some cars run hotter in the engine without causing a problem (knocking). Hotter (but not too hot), is better as it lets the engine pull that much more energy from the gasoline.

What it does with that extra energy depends on how the engine was designed and controlled. Nowadays, they have very sophisticated sensors and computer controls that allow for a range of operations. Maybe the engine utilizes the extra heat to get better mileage, maybe to get extra performance.
So it's conceivable that the higher priced, higher octane gas, also gets you higher mileage. Is it break even? That's even harder to say since your driving habits, weight of luggage, routes, weather, and even the direction of the wind, all also effect your mileage.
Or maybe it's how the designers made the car to go so fast, so quickly.

To answer the OP's specific question:
The best way to resolve this confusion is use the Sticker "EPA Fuel Economy Estimates, Annual Fuel Cost. That will be based on a LARGE number of variables, BUT, using the EPA tests means the calculations are standardized - so it IS valid for comparing them between two cars.
Bottom line: It's pretty much impossible to guess what your annual gas bill will be, but the above will give you a pretty good estimate of the difference between two cars.

02-14-2019, 01:43 PM
 Location: Saint Paul 887 posts, read 384,129 times Reputation: 1070
I compare cents per mile. For example, fuel costs \$2.40/gallon and vehicle gets 30 mpg, then it costs 2.40/30 so 8 cents per mile.

Another vehicle requires premium gasoline costing \$2.80 and gets 20 mpg. So \$2.80/20 equals 16 cents per mile.
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