Best speed for MPGs

Rahneld

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I'll bet it's been discussed and that many factors play into this, but on flat road, at about what speed does the 3.6JL maximize its fuel economy--at least one from the factory?

Speaking of factors: I wonder if the benefits of 8th gear, for example, might be counterbalanced by ones of the Wrangler's less than aerodynamic shape.

Of course, the question's academic. Thanks.
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liquids

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#1: If you're very concerned with mpg, get a manual. No contest.
#2: Way back in the days the the OPEC oil embargo, there were a lot of stories about 35-45 mph being the sweet spot for mileage, partly because you could hit maybe your highest gear around there while still not reaching the wind resistance to cancel that out. Wind resistance goes up with the square of your velocity.
 

wibornz

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#1: If you're very concerned with mpg, get a manual. No contest.
#2: Way back in the days the the OPEC oil embargo, there were a lot of stories about 35-45 mph being the sweet spot for mileage, partly because you could hit maybe your highest gear around there while still not reaching the wind resistance to cancel that out. Wind resistance goes up with the square of your velocity.
The manual is rarely as good on gas in the real world now adays. Drivers are lazy and do not shift when needed and the new auto transmissions with 7,8, or 10 gears always keeps the motor in the sweet spot. Times change.
 

Eloib

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I don’t think manuals are any better at consumption. The auto has 2 more gears, and you can (and should) drive it in sequential mode. I don’t understand people that just set it on D and go, specially considering that autos tipically do a pretty bad job at predicting when to downshift when the vehicle is slowing down (if they downshift at all)
 

UKCATS

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Anything over 80+mph is better. The faster you get there, the less time your engine runs and burns gas. It’s science.
 

NathanG

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Anything over 80+mph is better. The faster you get there, the less time your engine runs and burns gas. It’s science.
No.

At whatever speed range your car can shift into top gear and can maintain speed without bogging is gonna be the highest fuel mileage. The sweet spot is likely around 45-55. But who really cares as maintaining speed with traffic flow should be your priority for safety.

On a recent 400 mile trip to Los Angeles from AZ I found a 1-2 mpg drop by maintaining 80 vs 73- 75 with cruise control. This varies greatly with grade and headwind.
 

UKCATS

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No.

At whatever speed range your car can shift into top gear and can maintain speed without bogging is gonna be the highest fuel mileage. The sweet spot is likely around 45-55. But who really cares as maintaining speed with traffic flow should be your priority for safety.

On a recent 400 mile trip to Los Angeles from AZ I found a 1-2 mpg drop by maintaining 80 vs 73- 75 with cruise control. This varies greatly with grade and headwind.



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allieboy

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The best mileage comes from a brake check in front of a semi. After impact, I'm using the power of his truck to push me down the road. For that 1/10th of a mile I'm getting 27mpg!
 

JC7

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No.

At whatever speed range your car can shift into top gear and can maintain speed without bogging is gonna be the highest fuel mileage. The sweet spot is likely around 45-55. But who really cares as maintaining speed with traffic flow should be your priority for safety.

On a recent 400 mile trip to Los Angeles from AZ I found a 1-2 mpg drop by maintaining 80 vs 73- 75 with cruise control. This varies greatly with grade and headwind.
Pretty sure @UKCATS is right. You may want to check your "facts".
 

8flat

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The manual is rarely as good on gas in the real world now adays. Drivers are lazy and do not shift when needed and the new auto transmissions with 7,8, or 10 gears always keeps the motor in the sweet spot. Times change.
In town driving, yes this should be true.
Highway MPG should definitely be better in a manual though. The parasitic HP loss is wayyy lower in a manual. Seems like EPA just glosses over this, much like gearing differences. I guess they either don't test both transmission options, or gearing options?
 
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