I just asked my 15 year old son if he would be 15 minutes late for school if it allowed him to sleep an extra 15 minutes. He looked at me and said “Of course not. That’s stupid.”
Being late for work is simply not an option. And the reasons for that have nothing to do with fuel economy or saving money.
Well gee I remember the days of having to drive 55 on a freeway for 100 miles every day. The boss didn’t care if it took me an hour or an hour and a half. I still had to put my time in so any extra time used for travel was cutting into my time. OTOH whether I worked 8 hours or 10 or 12, I still got paid the same.
While it may not apply to all of us, TheWonderful90s is raising a valid point.
Along the lines of his argument, years ago a friend got his first job in a law firm in Boston. Instead of parking his car in the garage next door to the law firm, he chose a garage 2 blocks away because it was $15 cheaper per/day.
When his firm found out he was doing that, they ordered him to park in the more expensive garage next door. They said his “billable time” was more valuable to them than the time it took for him to walk those extra two blocks.
Power is Force over time or distance. Power lifting is NOT the correct term. It’s really Force lifting. They don’t take into account for the distance traveled or time.
Yup. I’ve turned down jobs in Boston (30 miles away) for a $50k/yr INCREASE because I’d be spending 2.5 - 5 hours a day traveling (depending on traffic that day). Most days would be closer to the 5 hour commute time. Not worth it.
Wow, that would be a soul crushing commute!
I get what the wonderful snowman is saying. It’s a concept, boys, not a literal “you make X dollars per hour”, although that’s how he’s choosing to put a value on it. It’s just a value of time…concept. And we must value our time at a similar rate to what we get paid…or else we wouldn’t be selling 40 plus hours a week of our life at that rate, right?
Look at it another way. Is the extra time spent dropping your speed while driving worth whatever you’ll save in money or fuel consumption? For me, it is not. The speed limit is 70, I drove 75 this AM and I’ll drive 75 back home. It’s sort of like buying gas at the cheapest place in town. Is the wait in line and the extra hassle and time spent worth the savings? That’s a big no, for me.
Funny thing, though, a lot of the same people who will wait in line to save ten cents per gallon when buying gas are the same people who will hit the interstate at 80 plus mph… 
I ran a test the other day with my Mustang. Flat highway, no wind. I set the cruise at the test speed and reset the mpg meter to zero each time and recorded the value after it settled out. Figure I drove roughly 2 miles each test.
65 mph… 24.7 mpg
70 mph… 23.7 mpg
75 mph… 21.3 mpg
80 mph… 20.0 mpg
So a 23% increase in speed decreases fuel economy 19%. Surprisingly close to linear. The curve fit equation is
Y= -0.003X^2 + 0.105X + 30.67 (that 30.67 is rolling resistance… wide tires likely responsible)
With an R^2 value of 0.977 (1.0 is a perfect fit)
Required energy to overcome wind resistance only (the square of the speed) would be 1.515 the energy consumption. The measured amount is 1.235. That’s just under half! So just under half of the fuel use difference is from aerodynamic drag. Then a significant portion must be linear from friction in the engine and drive train. Increased engine efficiency at higher load is another contributing factor, and with a bigger engine such as used in a Mustang it is a bigger factor than a small 3 or 4 cylinder economy car.
65 mph is 0.0405 gallons per mile
70 is 0.0422 +0.0017
75 is 0.0469 +0.0047
80 is 0.0500 +0.0031
It looks like there is a significant amount of error in the Mustang MPG test, probably due to differing road conditions and wind conditions, and not enough averaged repeated tests to get reliable numbers. The 70 to 75 MPH speed change had a fuel increase of 0.0047 which is a greater fuel increase than 75 to 80, which is 0.0031. That shouldn’t be the case and it is an error in excess of 50%.
Let’s say that 70 to 75 mph has a fuel consumption increase 0.0037 gallons per mile instead of 0.0047, because 0.0047 is obviously an error as it doesn’t correlate with the other numbers. 0.0037 at $4 per gallon gasoline is a cost increase of $0.0148 per mile. The time decrease is 0.000833 hours per mile. The cost of increasing speed is $17.76 per hour when driving the Mustang around 75 mph. If you slow down, every hour of increased travel time will save you about $18. If you work as a delivery driver and you bring in less than $18 per hour after all business expenses are paid, and you have flexible hours, and you have to commute to work as a delivery driver, you would be losing more money than you make at your job by driving faster. I used delivery driver as a job example since both the job and the commute involve driving, so the argument that the person enjoys driving more than doing their job can’t be made.
It seems to me that when the engine turns at a specific RPM level and my engine is at 2000 RPM and 70 MPH I use the same amount of fuel as I do if the car is moving at 25 MPH and 2000 RPM for each rotation. I can go almost 3 times as far on a gallon of gas at 70 though due to transmission gearing.
Internal friction in the engine accounts for something huge like 80% of the fuel use in that case. Keep your speed at 25 MPH and keep the throttle at the exact same spot and shift in to neutral. You’ll notice that the engine RPM doesn’t increase all that much with the load removed. That’s because nearly all of the fuel was used to overcome internal losses in the engine rather than putting out power.
When I go 55 at 2000 RPM and I shift in to neutral, the engine goes up to about 4500. That tells me that about half of the fuel used is overcoming internal losses in the engine. If the engine could be geared down to 1000 RPM my fuel economy should go from 33 MPG up to 44 since the wasted energy would drop to half, not taking in to account the lower thermal efficiency of the engine at lower speed. Switching from a 4 cylinder to a 2 cylinder engine should have the same effect.
Nope. Internal engine friction is a small part, nothing like half. The reason rpm’s jump a lot more at 55 than 25 is that the engine is under a lot more load, the throttle is further open.
Edit- from what I find, engine friction accounts for about 6% of the fuel used. The great majority of energy loss is heat, either out the exhaust or the radiator.
I am retired so cost per mile based on per-hour income is moot.
Every data point has error from a variety of locations. I’d prefer a minimum of 5 data points but driving at 60 in Florida is suicide. I’d be safer at 85. As I stated, there was no wind and the road was flat.
The lower speeds put me farther away from the lowest brake specific fuel consumption (BSFC) and the throttle is closed more so the pumping losses are higher. At 80 I am closer to the minimum BSFC and the throttle plate is open farther so pumping losses are reduced even though the aero drag is higher.
Those 2 improvements in the engine itself help to offset the 3rd order nature of the power curve to a significant degree.
And, yes, the 275/40/18 tires have a LOT of rolling resistance.
All I know is going faster saves time, and time is money.
That’s most likely at full throttle. You can get a good idea of how much friction there is by engine braking! In a manual you can turn off the engine and apply full throttle to get rid of the manifold vacuum drag to do an accurate test. Just don’t pull the key all they way out.
With current fuel prices and Interstate speed limits, your time has to be worth more than $10 or $20 an hour to justify driving faster!
Please do some research. Google ‘internal combustion energy efficiency’ and read up some to correct your mistaken opinions.
In addition to heat losses, read up on pumping losses, which increase at low load partial throttle conditions.
My time is definitely worth more than that. Isn’t yours 
Why
Was he showing up late and leaving early using the distance to the garage as an excuse
Like 2 blocks is a long walk
Because if he was getting there on time there is no way he can be forced to use the more expensive garage. Especial with that “billable” hours crap.
Knowing him, he wasn’t showing up late or leaving early.
He was forced to use the more expensive garage strictly because the firm could make more money off him if he got into the office a few minutes earlier.
More likely the named partners owned the parking garage.