# $4.50+ Gallon Gas and Mowing RPM



## Bob Driver (Nov 1, 2017)

By now, most of us have done the math to know what it cost to mow the lawn at $4.50+ a gallon for fuel. A big bore V-twin can get really thirsty, depending on your RPM setting. Most people will nail the throttle wide open and just go for it. That's a mistake, you're just wasting fuel, and making a lot more noise.

Working an engine is about peak torque, not about horsepower. The OEM's love to rate their engines in HP and they usually do that at WOT (Wide Open Throttle). However, as any truck driver will tell you, getting the most work out of an engine while using the least fuel is about managing the torque curve with the throttle.

Every OEM factory lawn mower service manual shows the torque curve for their engines. Most people never pay attention to it. Most engines are governed around 3,600 RPM. Most engines reach their max torque output between 2,800-3,000 RPM. If you want to use as little of that $4.50+ fuel as possible, look up the peak torque RPM on your engine and use that as your throttle setting to mow. Here's and example of what you'll see....

Below is the torque curve for a CV25 Kohler. Notice the engine torque (real power) starts to actually fall off above 3,000RPM. If you want to get the job done and use the least amount of fuel, running at 75%-80% governed throttle speed is your "sweet spot" for fuel economy


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## unsquidly (Jul 13, 2021)

Bob Driver said:


> Working an engine is about peak torque, not about horsepower. The OEM's love to rate their engines in HP and they usually do that at WOT (Wide Open Throttle). However, as any truck driver will tell you, getting the most work out of an engine while using the least fuel is about managing the torque curve with the throttle.
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Unless you are a company driver getting paid by the mile on a governed truck then it is "hammer down" to get as much speed as possible out if it to make max. $...................LOL


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## Bob Driver (Nov 1, 2017)

unsquidly said:


> Unless you are a company driver getting paid by the mile on a governed truck then it is "hammer down" to get as much speed as possible out if it to make max. $...................LOL


Last time we saw a fuel crunch like this, 68MPH on the governor, idle timers on, gear down protection set at 58MPH to force the knuckleheads to run in overdrive.


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## unsquidly (Jul 13, 2021)

Bob Driver said:


> Last time we saw a fuel crunch like this, 68MPH on the governor, idle timers on, gear down protection set at 58MPH to force the knuckleheads to run in overdrive.



With most larger type companies running automatics now it is way easier for them to "neuter down" the trucks to get as good of fuel millage as possible......Our lease trucks are set to 65 normal and 67 on cruise.....Our day cabs have 3 minute idle timers that can't be turned off by the driver.....Our sleeper trucks have apu on them and idle blocks buy you can bypass that by bumping the cruise.......I have a rental truck right now that is set to 70 and will idle forever if you bump the cruise.......LOL.......Right now, I only drive about 2,000 miles a week in 4 days but I am still going through about 3 grand a week at pump price in just the truck not counting the refer.........We just bumped our fuel surcharge to $55 per stop and getting ready to raise it again.........


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## Ultradog (Feb 27, 2005)

Bob Driver said:


> By now, most of us have done the math to know what it cost to mow the lawn at $4.50+ a gallon for fuel. A big bore V-twin can get really thirsty, depending on your RPM setting. Most people will nail the throttle wide open and just go for it. That's a mistake, you're just wasting fuel, and making a lot more noise.
> 
> Working an engine is about peak torque, not about horsepower. The OEM's love to rate their engines in HP and they usually do that at WOT (Wide Open Throttle). However, as any truck driver will tell you, getting the most work out of an engine while using the least fuel is about managing the torque curve with the throttle.
> 
> ...


Good advice Bob.
If you look at the old Nebraska Tests for tractors you will see torque and HP charts and computations for "horsepower hours per gallon" etc.
Most tractors attained 540 rpm pto speed at about 75-80% throttle. Maximum torque + maximum efficiency.
PS, 
Back in the early and mid 1980s I drove heavy trucks for a while and even OTR for a couple of years. Got fired twice.
Only times in my life I was even close to being fired.
I didn't like the work and I guess it showed. 😒


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## Bob Driver (Nov 1, 2017)

unsquidly said:


> With most larger type companies running automatics now it is way easier for them to "neuter down" the trucks to get as good of fuel millage as possible......Our lease trucks are set to 65 normal and 67 on cruise.....Our day cabs have 3 minute idle timers that can't be turned off by the driver.....Our sleeper trucks have apu on them and idle blocks buy you can bypass that by bumping the cruise.......I have a rental truck right now that is set to 70 and will idle forever if you bump the cruise.......LOL.......Right now, I only drive about 2,000 miles a week in 4 days but I am still going through about 3 grand a week at pump price in just the truck not counting the refer.........We just bumped our fuel surcharge to $55 per stop and getting ready to raise it again.........


Yep.... As an old timer once told me "Time to cinch down the cargo straps, it's 'bout to get rough for the next few miles"


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