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Speed for best fuel mileage

To get the best fuel economy what would be the fastest speed or top gear I should drive a FL Columbia with a C-15 475 HP, 3.55 rear end and 13 speed automatic transmission? or is there some sort of calculator online for this?

Thanks! :)

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13 Speed Auto ?? Is this a New truck/Transmission

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I was just asking about the 13 speed auto,I have not heard of it.

Yes,slower is better.

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I don't know if it really matters if the transmission is a manual or automatic. The slower the better when it comes to MPG's.

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Slower

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Thanks, I just thought I heard it mentioned that you can calculate the top speed you should go for certain specs.

Its an 09 Fliner but yeah it does have a 13 speed automatic unless an autoshift and automatic are different Ive been calling it an automatic. Im not wild about driving an auto but I have heard they get better fuel mileage sometimes u gotta do what u gotta do...

Since slower is better I guess its slow and easy down the road I go :)

Thanks for the replies

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I've got the same engine and gears with a 13spd overdrive. If mt or light, I drive in 13th gear at 1250RPM, and occasionally will split down to 12th on a hill when my RPM is pulled down below 1200, that being the bottom range of peak torque band. If the hills are constantly short rolling, I get lazy and leave it in 12th at 55mph; you have the advantage here with your automatic as it will shift back and forth perfectly every time for you. In the metro areas where the speed limit is 55mph, I will run along at 50mph in 12th. I think that 35 mph was the speed a truck drove at to achieve a record in mpg, but it's not very safe or time efficient to try and apply that style to the real world. Also, I've heard that there is no advantage to having a more aerodynamic truck at speeds below 52mph, so all else being equal, my Pete 379 vs a T660 should achieve equal fuel mileage at 51mph.

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The best answer is slower is always better. I have a C-15 with a 13 spd manual with 3.25 rears. and I have found that generally if I run at about 55 - 57 mph at about 1300 rpm I can usually stay in the low to mid 7 mpg range. how ever my fuel data has not shown that for the past month due to the excessive idle time because of running in texas, and the fact that I have had to run at a much higher than normal speed lately to meet the demands of the schedules of our customers.

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thanks for the great answers. That helps a lot.

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i had a similar setup and 59 at 1200 worked for me, but if you down shift to 12th gear it may help.

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cool thanks Eddy!

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Kathy Vonhatten will be eternally grateful.
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