When baseball player Alex “A-Rod” Rodriguez with the New York Yankees hits as many home runs as he did last season (16 to be exact), you know he has a winning technique for hitting the ball. A-Rod hits the ball at one of the “sweet spots” on his bat with almost every hit. Hitting the ball in this specific spot means he uses all of his energy of the swing towards pushing the ball the farthest it can go. For professional drivers, you win the game of trucking by driving at the sweet spot for your engine.
 
We know you’ve heard this time and again, slow down to get better fuel mileage, but it’s not that simple. Getting the best fuel mileage means finding the sweet spot – the best RPM to run your engine so it’s the most efficient. And with fuel costs consistently ranking as driver’s number one expense, the best way to save money on fuel costs is to find the sweet spot where your engine runs.

“The trick is pulling your load with torque and not horsepower,” says Bill McClusky, Business Consultant at ATBS. “When you pull with horsepower, you use more energy, and therefore burn more fuel to pull your load.”

Torque helps sustain speed when towing or maxing out your vehicle’s cargo capacity—especially in maintaining speed going up hills. If you know there’s a hill ahead, gain speed before you climb it. It will prevent you from shifting gears to get up the hill, using more horsepower.

Your dealer states peak horsepower and peak torque at specific RPM for each engine. Even though the RPM varies, we consistently found somewhere between 1250 - 1350 RPM is the magic number. The number not to exceed is 1500 RPM. You can contact your dealer to find the specifics for your engine and where your engine’s sweet spot is.

We aren’t telling you how fast you should drive, but if you want to save on fuel - finding that sweet spot can leave a sweet amount of savings in your checking account.

 
RPM What RPM do you run your truck at?
 
2%
 
16%
 
45%
 
25%
 
6%
 
4%

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Comment ()


I have 475 detroit. 10 spd. 65 mph im at 1300 rpms

August 01, 2016 15:28:52 PM

I get pretty good running down the road at 62mph (1350rpm) with a 13-speed OD manual, MBE4000 @ 435HP. I pull pneumatic tanker (older style J&L so not much for the aerodynamics) and the truck is a Western Star 4900FA. I usually weigh in around 79,000lbs loaded. I achieve 6.6 mpg on good running ground, but I suspect the lack of power is what makes my performance in the hills so poor. I always gear down before I hit the grades, but an example, running I-80 across Pennsylvania I usually am lucky to hit 5.9mpg. I've heard a lot of talk on the benefits of running in direct gear versus overdrive to achieve better fuel economy in hilly terrain, any thoughts? Also, I'm going to brag a bit, but 5.9mpg isn't breaking the bank, my fuel surcharge is usually calculated at 5mpg. But I'd love to get that number higher!

November 16, 2012 8:23:18 AM

I have run the same combination on the last four trucks I have ordered new, 500 hp Detroits, 13speed transmissions (last one is an ulltrashift two pedal) 3;73 reas on lo pro 24.5 rubber. I cruise at 57-59 mph, my first brake job was at 1,200,000 miles along with replacing kingpins. I have had one three axle alignment since the truck was new.

October 19, 2012 21:22:00 PM

Every time I read an article in Team Runsmart I learn something. I am so glad there is a site to learn from the Pro's.

September 23, 2012 12:12:53 PM

We have found that the Cummins ISX engine in a typical longhaul service duty type likes to run around 1375 to 1400 rpm for maximum fuel efficiency. The new ISX15 has a wider sweet spot range so I could certainly see the sweet spot rpm in the 1270 range. I do however question his recommendation of running 65 mph. The slower you run the less aero-dynamic drag resulting in improved mpg. You would have to be spec'd with 3:08 gears to run 1270 @ 65 mph. This axle ratio is typically used when specing a truck to run fast. Interesting recommendation.

September 16, 2012 23:40:21 PM

Cummins Representative came in yesterday and said for the ISX15, 1270RPM @ 65MPH is the most fuel efficient. Also, he said to expect a 1% increase in Fuel Economy with every 100RPM decrease.

September 11, 2012 9:00:59 AM

If the Freightliner engineers can think of any more factors that influence a trucks' fuel mileage, please add them in.

September 04, 2012 8:33:39 AM

Great list, Rick. Team Run Smart might need to steal...errr...borrow...some of these :)

September 04, 2012 7:19:22 AM

Okay Grant, here you go. I couldn't remember all but I've got most of them.

Mechanical (Controllable)

DRIVER (jack rabbit takeoffs etc., Smith System)) the number varies but can be as much as a difference of 30-40% of a truck's mileage

Speed Leaking Charge Air Cooler Overhead (valves) out of adjustment
Idling Tire rolling resistance Tire air pressure
Tire type (LP and wide singles vs. tall rubber)
Rear end gears (proper gears for the speed you usually drive at)
Horsepower setting Engine oil (mineral vs. synthetic)
Air gap (between tractor and trailer) Mufflers (Full baffle vs. flow thru)
Progressive shifting (turn on in truck computer)
Revolutions per mile (specific to your tire size in truck's computer)
Cruise control setting in truck's computer
Transmission choice (manual vs. auto or semi auto)
Truck alignment
Trailer alignment
Dirty air filters
Correct fuel and air filters (proper flow rate)

Use of devices such as GPS for proper routing saves fuel on lost miles
Other devices such as Turbo 3000 and Airtabs have helped SOME trucks

Mechanical (Uncontrollable)

Aerodynamics of truck (Classic vs. Cascadia)
Engine Make (Detroit vs. CAT)
Type of trailer (dry van vs car hauler etc.)
Weight of Load
Weather
Road surface (asphalt vs. concrete)
Terrain (climbing hills vs. flat road)
Type of Driving (Highway vs. city e.g. traffic lites, starting/stopping etc.)

It's a accumulative thing. The more of these factors you can overcome, the better your fuel mileage will be. The quickest and cheapest (no cost) are to slow down, stop idling, computer settings (my shop does not charge me), air gap, After that i would check my charge air cooler for leaks and after that I would run the overhead. You can get into things like tires and mufflers when they need to be replaced unless you want to spend the money sooner. Tires is one of those things that pay for themselves in fuel savings if you don't wait.
I hope this helps.

August 31, 2012 13:18:27 PM

To Rick Ash: can you get your friend's 30 factors? Those would be great to share...

August 29, 2012 8:20:57 AM

To Andrew Letts: Need a little more information. What engine is in your truck? I can give you a good starting point based on engine type and service duty type.

August 27, 2012 9:49:54 AM

To John Taylor: Road speed to engine rpm is determined by a number of factors, axle ratio, tire diameter, transmission out put ratio and the corresponding settings in the ECM. I would be very interested in knowing what your axle gear ratio and tire size is. There are settings in the ECM for "revolutions per mile" for the tires you are using, and settings for "transmission output ratio" and "axle gear ratio". The ECM uses these settings along with information from various sensors to calculate and display information to the driver and to log trip activity information to the ECM. If any of the ECM settings are incorrect you could be getting an incorrect speed reading. The axle ratio is usually on the tag located on the door jam. Has the transmission or differentials ever been replaced?

August 27, 2012 9:43:34 AM

A good friend once told me that there are more than 30 different factors that can influence your fuel mileage. A large number of them are controllable such as speed, driving tactics, gear ratios, tires with low rolling resistance etc. Some are not controllable such as weather and the kind of road surface you are driving on. The more changes you are willing to make with the "controllables", the better your fuel mileage will get. It takes a lot of pieces to complete the puzzle.

August 21, 2012 7:49:15 AM

Ok, I have a problem with this article. I have a 06 Freightliner Columbia, just under 700k miles. Detroit Series 60 14 liter, with an Eaton 10 speed, Not sure about the rears. The problem is everyone says not to run over 1500 rpm. I've driven this truck since it was new and recently purchased it. The manufacturer says peak horsepower is at 1800 rpm. I know pull with torque not horsepower. But even at 55 in 10 gear, this truck has always pulled ove 1400 rpm, run up to 60 and your about 1550 rpm. 61 gets you just under 1600. Freightliner has looked at it and says nothings wrong. My question is how do you drive slow enough to get down to 1350 rpms. or what mods do I need to do on my truck?

August 20, 2012 9:05:52 AM

good article...yes keep the RPM's in the sweet spot and boost down helps fuel mileage.

August 16, 2012 18:19:42 PM

i have 2007 frght century with bridgestone 720 i cnt find the sweet spot

August 04, 2012 20:04:32 PM

There r so many different ways things you can do to find your sweet spot...problem is finding out what's right for you and your truck

August 04, 2012 13:14:13 PM

I am not sure where the sweet spot is on my truck yet; but I do know if I run at 55 mph I achieve 8.1 mpg. That is sweet enough for me!

August 03, 2012 21:44:10 PM

Steroids help too!

August 03, 2012 10:42:33 AM

In addition to tire size another important factor is choosing a tire with the lowest rolling resistance.

July 29, 2012 14:23:38 PM

Drive axle gear ratios and drive tire size are 2 critical components in matching desired road speed to engine rpm sweet spot. These specs are commonly overlooked by used truck buyers.

July 26, 2012 14:32:09 PM

Nice illustration. The key is finding the sweet spot for each truck individually and not choosing your ideal speed because that's what your buddy recommended. Great information!

July 26, 2012 12:07:19 PM

There may be a learning curve in determining where the sweet spot is in a new truck. It could take on the average 50K to 75K miles to determine this.

July 26, 2012 12:01:55 PM

Shweet! :)

July 26, 2012 10:48:00 AM

Heather, where did you learn so much about trucking?

July 26, 2012 8:14:53 AM

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About Bill McClusky

I have been in the trucking and construction equipment service industry for 23 years as a service technician, component rebuild specialist (engine, transmission, and axle), service department manager, instructor and consultant. I was a class 8 truck driver for 3 years pulling wet and dry tanks. I have been with American Truck Business Services for 4 years serving as a Business Consultant, Maintenance Consultant, and Instructor.

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