Some simple math regarding fuel economy

Stone Express · Jun 10, 2014

I believe the drag at 75 verses 60, is much greater than 56%. I do not have the drag formula at the moment, but remember that the difference between 55 and 65 is 66%. It goes up dramatically from there. The drag at 70 is at least twice that of 55........ but of course I have been known to be wrong.

EZX1100 · Jun 10, 2014

flightwatch said: ↑

I was inspired to write this thread by the recent threads regarding fuel economy and governed trucks. I wanted to show you all exactly why companies govern their trucks, and why the smart owner operator will slow down. I will show you how you could actually make more money by driving slower. Not to mention being less stressed out, having more free time, and just generally being happier.

This scenario will assume a .4mpg difference from 62 mph truck and a 65 mph truck where the 62mph truck gets 7.2 mpg and the 65 mph truck gets 6.8 mpg. It will also assume an average fuel cost of $4/gal and averaging a 10 hour drive day.

Truck 'A': 62mph and 7.2mpg's

miles driven 620. Fuel used: 86 gallons at a cost of $344

Truck 'B': 65 and 6.8mpgs

miles driven 650. Fuel used: 96 gallons at a cost of $382

At the end of 1 day, Truck B drove drove 30 more miles, but spent $38 more in fuel.

By the end of the week, truck B drove 210 more miles, but spent $268 more in fuel.

At the end of a 31 day month, truck B has driven 930 miles more than truck A at 62 mph, but that fuel cost you an extra $1178

That is $14,136.00 extra a year you are spending in fuel for a .4 mpg decrease in economy and 3 mph.

That's more than some people make in a year.

Now for an extreme

At 75mph and 5mpg: You all will drive 4030 miles more in a 31 day month than that 62 mph truck, but it'll cost you an extra $16,120.00 in fuel

At the end of 12 months, you have put an extra 48,000 miles on your truck and spent an extra $193,440.00 in fuel. That means that every single load that Mr. super trucker ran for that year would have had to pay out $4.03/mile just for him to break even with the 62mph driver. Let's put it this way. The 62mph driver had to drive 48,000 miles less than super trucker...yet they both made the same amount of money. The 62 mph driver had more free time and was less stressed out because he was at home relaxing while the super trucker was still out running that $4/mile load.

I see it and hear it time and again; "I can get 7 mpg's at 75 mph." No you can't, and you're only fooling yourself. I don't care how the truck is spec'd. Drag will kill you at those speeds. Without getting into some pretty deep math, a truck has to produce 176% more effort to drag itself down the road at 75 than at 62. Wind resistance and drag are exponential. An aerodynamic truck will get its best fuel economy at around 52-54 mph. That is why all those slow ### Prime trucks are getting 9-10 mpg while you blow their doors off.

This is why companies govern their trucks. That is also why they spec their trucks with 425hp ISX engines mated to 8 speed transmissions and balanced rear ends. But the #1 spec any driver can do for their truck (and their wallet) is to slow down.
Click to expand...

why not drive 45mph and get 10mpg

think of all the money you will save

Hauling365 · Aug 16, 2016

flightwatch said: ↑

I was inspired to write this thread by the recent threads regarding fuel economy and governed trucks. I wanted to show you all exactly why companies govern their trucks, and why the smart owner operator will slow down. I will show you how you could actually make more money by driving slower. Not to mention being less stressed out, having more free time, and just generally being happier.

This scenario will assume a .4mpg difference from 62 mph truck and a 65 mph truck where the 62mph truck gets 7.2 mpg and the 65 mph truck gets 6.8 mpg. It will also assume an average fuel cost of $4/gal and averaging a 10 hour drive day.

Truck 'A': 62mph and 7.2mpg's

miles driven 620. Fuel used: 86 gallons at a cost of $344

Truck 'B': 65 and 6.8mpgs

miles driven 650. Fuel used: 96 gallons at a cost of $382

At the end of 1 day, Truck B drove drove 30 more miles, but spent $38 more in fuel.

By the end of the week, truck B drove 210 more miles, but spent $268 more in fuel.

At the end of a 31 day month, truck B has driven 930 miles more than truck A at 62 mph, but that fuel cost you an extra $1178

That is $14,136.00 extra a year you are spending in fuel for a .4 mpg decrease in economy and 3 mph.

That's more than some people make in a year.

Now for an extreme

At 75mph and 5mpg: You all will drive 4030 miles more in a 31 day month than that 62 mph truck, but it'll cost you an extra $16,120.00 in fuel

At the end of 12 months, you have put an extra 48,000 miles on your truck and spent an extra $193,440.00 in fuel. That means that every single load that Mr. super trucker ran for that year would have had to pay out $4.03/mile just for him to break even with the 62mph driver. Let's put it this way. The 62mph driver had to drive 48,000 miles less than super trucker...yet they both made the same amount of money. The 62 mph driver had more free time and was less stressed out because he was at home relaxing while the super trucker was still out running that $4/mile load.

I see it and hear it time and again; "I can get 7 mpg's at 75 mph." No you can't, and you're only fooling yourself. I don't care how the truck is spec'd. Drag will kill you at those speeds. Without getting into some pretty deep math, a truck has to produce 176% more effort to drag itself down the road at 75 than at 62. Wind resistance and drag are exponential. An aerodynamic truck will get its best fuel economy at around 52-54 mph. That is why all those slow ### Prime trucks are getting 9-10 mpg while you blow their doors off.

This is why companies govern their trucks. That is also why they spec their trucks with 425hp ISX engines mated to 8 speed transmissions and balanced rear ends. But the #1 spec any driver can do for their truck (and their wallet) is to slow down.
Click to expand...

First off in your scenario sounds like they are running year round with no vacations so using the same numbers as you. I have taken the trouble of finishing what you started doing. So here would be your year's total.....
63mph... drives 230640 miles thats 32033.33 gallons of fuel costing you $128133.33
65mph... drives 241800 miles thats 35558.82 gallons of fuel costing you $142235.29
75mph... drives 279000 miles thats 55800 gallons of fuel costing you $223200
Here comes the part you happened to leave out. If the loads pay $4.03/miles...
63mph... gross income $929479.20 minus fuel leaves you with $801345.67
65mph... gross income $974454 minus fuel leaves you with $832218.71
75mph... gross income $1124370 minus fuel leaves you with $901170

So at the end of the year... 75mph makes $99824.33 more than 63mph and $80964.71 more than 65mph after fuel. So in the same time of working(10 hour days) 75mph has earned almost $100k more than 63mph. Huh sounds to me like 63mph is just a fat, lazy slob that all he knows how to do is cause a traffic jam when it takes him 3 miles to pass the slow lazy slob in front of him. No thanks I got places to go and people to see. Why do you think owner operator are the only ones that can go 75mph they can afford to fix their truck. 63mph company drivers will always earn alot less than someone who can go faster. Companies govern their trucks at 63mph to save that little bit of change from fuel and maintenance, because that means the big wigs upstairs get to keep more of the drivers hard earned money and spend it on their own toys. So while you are crawling down the road at 63mph and a Prius passes you just think what kind of toy your boss is going to buy.

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