This thread and this site inspired (or prompted) this thread.
People are always telling you ways to save money on gas and one way I hear often is to slow down. This, of course meaning on the freeway/highway. But, what most people don't think enough about is that by slowing down, you also lose time, which is of (greater, I believe) value than money.
Here's an example which will lead to a not-too-difficult formula:
Put a value on your time. Let's say $15/hr is what you determine. (Some of you may think this is too low, a few may think it's too high - adjust accordingly then.)
And, again a gross simplification, our gas costs $3 per gallon.
Say driving at 60 mph, your car's fuel efficiency is 25 mpg.
Then, a 30 mile trip would take half an hour (30 mi/60 mph) and would use 1.2 gallons of gas (30 mi/25 mpg).
So, $15/hr*(.5 hr) + 1.2 gal*$3/gal = $7.5 + $3.6 = $11.1
The trip costs you $11.10.
And now, let's be conservative and put your car's performance at 22 mpg at 70 mph (these numbers won't be as pretty).
A 30 mile trip would take 26 minutes (.43 hr = 30 mi/70 mph) and consume 1.4 gallons of gas (30 mi/22 mpg).
$15/hr*(.43 hr) + 1.4 gal*$3/gal = $6.43 + $4.2 = $10.6
The trip costs you $10.60.
Yes, this calculation requires some estimation/fudging, but I'm pretty sure those mpg numbers are a lot closer than I've put them, but perhaps not. And realize that these numbers worked in a speeders' favor for this example; if you had a gas-guzzling SUV or lower value on your time or gas prices were higher, then driving slower might really save you money. This is just something to think about.
As far as a formula goes, it's not too complicated:
h = the value you put on your time
g = fuel cost (per unit)
d = distance covered (this is a constant, so it's not even necessary in the calculation for comparison)
r1 = rate/speed/velocity for calculation #1
r2 = rate/speed/velocity for calculation #2
f1 = fuel efficiency for calculation #1
f2 = fuel efficiency for calculation #2
Calculation #1 Cost = h*d/r1 + g*d/f1
Calculation #2 Cost = h*d/r2 + g*d/f2
Remember, the objective is to minimize costs, or "save you money" (it's the reason driving slower sounded good in the first place, right?).
I know somehow, speed and fuel efficiency are related (above a certain speed, fuel efficiency starts decreasing, faster and faster, too), but I don't know the relation, so you just have to estimate.
In conclusion, this thread is not an encouragement for people to start driving like maniacs (I'm not even advocating anyone driving faster at all), but just a counterbalance to all the people who love to tell you that driving slower saves you money.
People are always telling you ways to save money on gas and one way I hear often is to slow down. This, of course meaning on the freeway/highway. But, what most people don't think enough about is that by slowing down, you also lose time, which is of (greater, I believe) value than money.
Here's an example which will lead to a not-too-difficult formula:
Put a value on your time. Let's say $15/hr is what you determine. (Some of you may think this is too low, a few may think it's too high - adjust accordingly then.)
And, again a gross simplification, our gas costs $3 per gallon.
Say driving at 60 mph, your car's fuel efficiency is 25 mpg.
Then, a 30 mile trip would take half an hour (30 mi/60 mph) and would use 1.2 gallons of gas (30 mi/25 mpg).
So, $15/hr*(.5 hr) + 1.2 gal*$3/gal = $7.5 + $3.6 = $11.1
The trip costs you $11.10.
And now, let's be conservative and put your car's performance at 22 mpg at 70 mph (these numbers won't be as pretty).
A 30 mile trip would take 26 minutes (.43 hr = 30 mi/70 mph) and consume 1.4 gallons of gas (30 mi/22 mpg).
$15/hr*(.43 hr) + 1.4 gal*$3/gal = $6.43 + $4.2 = $10.6
The trip costs you $10.60.
Yes, this calculation requires some estimation/fudging, but I'm pretty sure those mpg numbers are a lot closer than I've put them, but perhaps not. And realize that these numbers worked in a speeders' favor for this example; if you had a gas-guzzling SUV or lower value on your time or gas prices were higher, then driving slower might really save you money. This is just something to think about.
As far as a formula goes, it's not too complicated:
h = the value you put on your time
g = fuel cost (per unit)
d = distance covered (this is a constant, so it's not even necessary in the calculation for comparison)
r1 = rate/speed/velocity for calculation #1
r2 = rate/speed/velocity for calculation #2
f1 = fuel efficiency for calculation #1
f2 = fuel efficiency for calculation #2
Calculation #1 Cost = h*d/r1 + g*d/f1
Calculation #2 Cost = h*d/r2 + g*d/f2
Remember, the objective is to minimize costs, or "save you money" (it's the reason driving slower sounded good in the first place, right?).
I know somehow, speed and fuel efficiency are related (above a certain speed, fuel efficiency starts decreasing, faster and faster, too), but I don't know the relation, so you just have to estimate.
In conclusion, this thread is not an encouragement for people to start driving like maniacs (I'm not even advocating anyone driving faster at all), but just a counterbalance to all the people who love to tell you that driving slower saves you money.