How to Get the Most Fuel Economy

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799
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Alaska and Wisconsin
Lady at church still drives that original Excursion diesel …
I can remember when it was full of Little League players.
Drove one of those as a work truck along the northern 1/3 of the Trans-Alaska Pipeline System (TAPS), maintaining the fiber-optic network along it. Put 20K miles on it along the same stretch of road the Ice Road Truckers did and liked it. The only thing I disliked was the front suspension didn't have enough travel -- I bottomed it out many many times on potholes along the Dalton Hwy, otherwise known as the "Haul Road" to the North Slope oil fields. Also drove F-350 and Chevy 2500 diesel trucks as needed. All were good trucks as they were properly outfitted and expertly maintained by fantastic mechanics at pump stations #1 and #5.

Bar none, for a good living I drove and operated the most remote and loneliest stretch of road in North America. No services of any kind for 241 miles between Coldfoot, Alaska and Deadhorse, Alaska... no services, no lights, no fences, no sign that Man has ever been there except for the pipeline and a few related pump stations, associated remote gate valves and the gravel road highway. It was absolutely a vast and beautiful sub-arctic and arctic wilderness full of mountains, sub-arctic forests, arctic tundra, and animals.

Note that as a Alyeska pipeline contractor, I had access to services at Alyeska pump stations positioned about every 60 to 70 miles along the pipeline. Fueled up and ate like a king at those along the way. Your average civilian venturing that far north didn't have any access to those.
 
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2,012
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.
Conditions and safety permitting, rpm @45-50% of red line is the most efficient engine speed to run at (or torque peak).

That explains why fuel economy constricted OEMs program engines with a 6,500 rpm redline to run at c. 2,000 at freeway speeds.
 
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17,214
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...
Drove one of those as a work truck along the northern 1/3 of the Trans-Alaska Pipeline System (TAPS), maintaining the fiber-optic network along it. Put 20K miles on it along the same stretch of road the Ice Road Truckers did and liked it. The only thing I disliked was the front suspension didn't have enough travel -- I bottomed it out many many times on potholes along the Dalton Hwy, otherwise known as the "Haul Road" to the North Slope oil fields. Also drove F-350 and Chevy 2500 diesel trucks as needed. All were good trucks as they were properly outfitted and expertly maintained by fantastic mechanics at pump stations #1 and #5.

Bar none, for a good living I drove and operated the most remote and loneliest stretch of road in North America. No services of any kind for 241 miles between Coldfoot, Alaska and Deadhorse, Alaska... no services, no lights, no fences, no sign that Man has ever been there except for the pipeline and a few related pump stations, associated remote gate valves and the gravel road highway. It was absolutely a vast and beautiful sub-arctic and arctic wilderness full of mountains, tundra and animals.

Note that as a Alyeska pipeline contractor, I had access to services at every Alyeska pump station positioned about every 60 to 70 miles along the pipeline. Fueled up and ate like a king at those along the way. Your average civilian didn't have any access to those.


I had to look up Deadhorse Alaska as I thought it was in the Yukon. That would be Whitehorse.

My iPhone says it is -22F in Deadhorse. Time for 0wxx
 
Messages
799
Location
Alaska and Wisconsin
I had to look up Deadhorse Alaska as I thought it was in the Yukon. That would be Whitehorse.

My iPhone says it is -22F in Deadhorse. Time for 0wxx
Every fluid used in North Slope-related vehicles sports cold-rated synthetic oils, greases, and other fluids. They are typically changed ahead of the severe schedule. My driven trucks had fluids changed once a month! One cannot afford a mechanical breakdown in such an austere and severe environment.

Here's an example of a competitor's (AT&T) diesel Excursion on the North Slope. Note the woman pictured was killed in a rollover accident on the Slope. She was known as a careful driver and was missed within the Slope work community.

Competitor's Vehicle.JPG


This summertime picture was taken at a pulloff in the Brooks Range.
 
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795
Location
98245
Conditions and safety permitting, rpm @45-50% of red line is the most efficient engine speed to run at (or torque peak).
That depends on how much output (power / torque) you need from the engine. At full throttle, peak torque is the RPM having maximum BMEP, but that is not the same thing as minimum BSFC (peak efficiency), which varies depending on load or power output. On most gasoline engines, peak torque RPM is not the most efficient for low power cruise. Peak torque RPM can be pretty high (like 4,000 RPM in my Mazda). I can guarantee you that cruising down the freeway at 4,000 RPM in my Mazda means being in 4th gear where it gets much worse fuel economy than in 6th gear.

Part of what you say is correct: the RPM at which the engine achieves max efficiency is near peak torque at wide open throttle. But that's more power than you need. To cruise at 60 mph you need to dial back the power. There are 2 ways you can do that:

1. Keep the engine at peak torque RPM and dial back the throttle.
2. Use a taller gear to reduce RPM and keep the throttle open.

When the amount of power you need is less than what the engine can deliver, method (2) is a more efficient way to reduce power. That's why cars have tall overdrive gears for freeway driving. And why CVTs in "normal/economy" mode keep the engine at revs far below peak torque.
 
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811
Location
sw ohio
That depends on how much output (power / torque) you need from the engine. At full throttle, peak torque is the RPM having maximum BMEP, but that is not the same thing as minimum BSFC (peak efficiency), which varies depending on load or power output. On most gasoline engines, peak torque RPM is not the most efficient for low power cruise. Peak torque RPM can be pretty high (like 4,000 RPM in my Mazda). I can guarantee you that cruising down the freeway at 4,000 RPM in my Mazda means being in 4th gear where it gets much worse fuel economy than in 6th gear.

Part of what you say is correct: the RPM at which the engine achieves max efficiency is near peak torque at wide open throttle. But that's more power than you need. To cruise at 60 mph you need to dial back the power. There are 2 ways you can do that:

1. Keep the engine at peak torque RPM and dial back the throttle.
2. Use a taller gear to reduce RPM and keep the throttle open.

When the amount of power you need is less than what the engine can deliver, method (2) is a more efficient way to reduce power. That's why cars have tall overdrive gears for freeway driving. And why CVTs in "normal/economy" mode keep the engine at revs far below peak torque.
Thanks. Interesting. That BMEP is the point where fuel efficiency is greatest per horsepower and is independent of wide open throttle position?

You are correct but I spoke of max efficiency regardless of what is needed or appropriate -no preconditions. Just max efficiency. Period.
 
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112
Location
Virginia
“Also on moderate hills, if you can keep the pedal steady and bleed off some speed to reach the top, this saves quite a bit compared to maintaining your speed exactly.”

Years ago I kept the cruise control on while on the highway thinking it would give me the best MPG. Wrong. It’s OK for straight and level. I found that slowing loosing some speed going up a grade then slowing getting back up to speed on the downhill side gave better fuel economy in hilly areas.
I think I did the opposite - Durango Richmond to Charlottesville.
Cruise on, I would take the 'free' acceleration down a hill - say to 20 above limit at bottom of valley, but slowly with very light pedal and then hold that foot position until CC took back over again near top. Took some effort, but I think it saved w/o holding anyone up.
 
Messages
795
Location
98245
...I spoke of max efficiency regardless of what is needed or appropriate -no preconditions. Just max efficiency. Period
Yeah, that's how I interpreted what you said.

Interesting. That BMEP is the point where fuel efficiency is greatest per horsepower and is independent of wide open throttle position?
Ay, there's the rub. It's not independent, it is very dependent. Peak efficiency, or minimum BSFC, depends on load or power output. If the engine produces 100 HP at its peak torque RPM at full throttle, then this is the most efficient combination of RPM and throttle that produces 100 HP, which is minimum BSFC for 100 HP. But if all you need is 30 HP, it is most efficiently produced at a much lower RPM.

A constant power curve can be useful for illustrating this, as discussed here.
 
Messages
811
Location
sw ohio
Yeah, that's how I interpreted what you said.


Ay, there's the rub. It's not independent, it is very dependent. Peak efficiency, or minimum BSFC, depends on load or power output. If the engine produces 100 HP at its peak torque RPM at full throttle, then this is the most efficient combination of RPM and throttle that produces 100 HP, which is minimum BSFC for 100 HP. But if all you need is 30 HP, it is most efficiently produced at a much lower RPM.

A constant power curve can be useful for illustrating this, as discussed here.
Thanks for the link. Interesting read. Much better than "what is the best oil" or "I'm tearing my hair out: 5-30 or 10-30" LOL
 
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5,755
Location
the canyons
Every fluid used in North Slope-related vehicles sports cold-rated synthetic oils, greases, and other fluids. They are typically changed ahead of the severe schedule. My driven trucks had fluids changed once a month! One cannot afford a mechanical breakdown in such an austere and severe environment.

Here's an example of a competitor's (AT&T) diesel Excursion on the North Slope. Note the woman pictured was killed in a rollover accident on the Slope. She was known as a careful driver and was missed within the Slope work community.

View attachment 50268

This summertime picture was taken at a pulloff in the Brooks Range.
RIP, Joy.
 
Messages
2,902
Location
Northeast
'18 Hyundai Accent SE w/ 6 speed auto . Warmer weather helps . Fill up yesterday of winter blend Top Tier VALERO 90 non E @ 1 click . Tires are CONTINENTAL Pro Contact TX (H) @ 34 > 35 P.S.I. with 7 > 8/32s' of tread . Doubt I'll be able to keep over 50 m.p.g.. Best was 45 calculated . Oil is SHELL Rotella Gas Truck 5w-30 ( SN+) and Fram Ultra XG9688 . All oil before was Pennzoil Platinum 5w-20 . No difference in fuel economy .

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