Mathmanmathmanmathman
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So, one of my friends posted this on Facebook today:
______ is pondering this fact: each 5 mph you drive OVER 60 mph is like paying $.10 extra per gallon.....discuss
Firstly, let's stipulate that this fact is true, though I'll address this later...
That made me first think, "Holy crap... maybe I really shouldn't go 75 or so then." But then I decided to do the math, and came up with this to response:
I suppose it depends on what you think your time is worth. If (broad estimate here) average mpg is 19.8 for cars and light trucks, let's say (for ease of math) you're going 65 miles. If you go 60mph, no additional cost, but an extra 5 minutes. If you go 65mph, you gain $.10 per gallon. With average 19.8 mpg for 65 miles, that's using 3.28 gallons, equaling 32.8 cents you've cost yourself. If that's for 5 minutes, that means you cost yourself $3.94 to gain an hour for going only 5mph over 60. So as long as you consider your time worth more than ~$4/hour, you should eat the cost of the extra 5mph.
Using the same system (but say you're going 70 miles for 70pmh), you're now costing yourself $4.24 per hour. $4.54/hr for 75mph, $4.84/hr for 80mph... effectively an additional 30 cents per hour for every additional 5mph over.
So basically, if I'm going, oh, 300 miles, it'll take me 4 hours going 75mph and 5 hours going 60mph. But to gain that hour, I'll spend $4.54. So is gaining an hour worth $4.54? It seems to me in most cases it would be.
However, in looking up to verify the fact, two things occurred to me.
Firstly, the number varies greatly in what I'm finding. My friend said 10 cents. I'm seeing 24 cents a lot of places. Some sites list it as high as 51 or 54 cents. 54 cents?! That's over $21/hr! So I'm dubious of this number. And rightfully so...
Secondly, it occurred to me the cost can't be stated blankly like such! The cost of gas established by the stations is a completely independent variable as to the amount of gas burned by increased rate of speed. But it seems reasonable that there would exist a speed at which one's engine runs at optimum efficiency (like 60, per chance), and that to go faster than that would decrease the efficiency of the gas consumption. So to be more accurate, one would need to establish the increased percentage of gas consumed per mile spent going at a particular rate over the optimum speed, and extrapolate the equivalent cost based on the current gas prices of the day. But then you probably end up spending as much time calculating the amount saved as the time you would have saved ignoring the amount saved.
At any rate, the math intrigued me. Thoughts? Also, please let me know if you see any errors in logic or math I might have made. I'd deserve it for watching TV while posting and doing math.
TL;DR: Just speed.
-Willlo
So, one of my friends posted this on Facebook today:
______ is pondering this fact: each 5 mph you drive OVER 60 mph is like paying $.10 extra per gallon.....discuss
Firstly, let's stipulate that this fact is true, though I'll address this later...
That made me first think, "Holy crap... maybe I really shouldn't go 75 or so then." But then I decided to do the math, and came up with this to response:
I suppose it depends on what you think your time is worth. If (broad estimate here) average mpg is 19.8 for cars and light trucks, let's say (for ease of math) you're going 65 miles. If you go 60mph, no additional cost, but an extra 5 minutes. If you go 65mph, you gain $.10 per gallon. With average 19.8 mpg for 65 miles, that's using 3.28 gallons, equaling 32.8 cents you've cost yourself. If that's for 5 minutes, that means you cost yourself $3.94 to gain an hour for going only 5mph over 60. So as long as you consider your time worth more than ~$4/hour, you should eat the cost of the extra 5mph.
Using the same system (but say you're going 70 miles for 70pmh), you're now costing yourself $4.24 per hour. $4.54/hr for 75mph, $4.84/hr for 80mph... effectively an additional 30 cents per hour for every additional 5mph over.
So basically, if I'm going, oh, 300 miles, it'll take me 4 hours going 75mph and 5 hours going 60mph. But to gain that hour, I'll spend $4.54. So is gaining an hour worth $4.54? It seems to me in most cases it would be.
However, in looking up to verify the fact, two things occurred to me.
Firstly, the number varies greatly in what I'm finding. My friend said 10 cents. I'm seeing 24 cents a lot of places. Some sites list it as high as 51 or 54 cents. 54 cents?! That's over $21/hr! So I'm dubious of this number. And rightfully so...
Secondly, it occurred to me the cost can't be stated blankly like such! The cost of gas established by the stations is a completely independent variable as to the amount of gas burned by increased rate of speed. But it seems reasonable that there would exist a speed at which one's engine runs at optimum efficiency (like 60, per chance), and that to go faster than that would decrease the efficiency of the gas consumption. So to be more accurate, one would need to establish the increased percentage of gas consumed per mile spent going at a particular rate over the optimum speed, and extrapolate the equivalent cost based on the current gas prices of the day. But then you probably end up spending as much time calculating the amount saved as the time you would have saved ignoring the amount saved.
At any rate, the math intrigued me. Thoughts? Also, please let me know if you see any errors in logic or math I might have made. I'd deserve it for watching TV while posting and doing math.
TL;DR: Just speed.
-Willlo