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gear ratio and 10 speed trans

My Volvo V12 has a gear ratio of 3.58 and a 10 speed trans. Low pro file tires. Can some one tell me what the magic mph number is for best mpg. I have been told that I could find it on this forum but have not found it any where yet.

Answer this question I have this problem too

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58 to 62 depending on weight,hills,weather

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Thanks Tony, I will try 58 and see what happens. I have done 62 for ever and for ever been at 5.75 mpg.

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I don't know the volvo engine but 58-62 is going to put it at low rpm and I doubt that the tiny 12L engine has enough torque for that.

What's your mpg at 65mph? That's the speed your truck is geared for.

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Just looked up some info on your engine and recommended cruise rpm is 1400-1600. If you can keep close to 1500 rpm with minimum throttle you should get better fuel economy. That may be somewhat hindered by the fact that you have dual egr though. I also read that you have 2 full flow and 1 bypass oil filters which should give your engine a long life. Here's some extra maintenance info: http://www.thetruckersreport.com/truckin...

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Jerzy Zaleski, I am not sure what the mpg is at 65mph I have never tried it but you are the first to tell me that my truck is geared for that of 65mph. At 62 mph for the past yr I am at 5.75. I guess if I drive faster then I will do better from what you are saying.

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Well...maybe or maybe not. I'm going by how my truck runs with similar gears. At 64-65mph i'm around 1475rpm and i can maintain that speed with very light throttle which helps my mpg. If i could run 58-60mph with as little throttle i would get better mpg however that puts me at low rpm and with any hills or wind resistance requires more boost which drops my mpg. Try 64-65 mph and see what happens. You can also buy the scangauge d which is fantastic for learning how to get mpg on any truck.

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I have a 2006 D12 Volvo 780 and it is loaded to the max most of the time.

I-10, I-65, I-75 to Florida then I-4 to I-10 back to Louisiana, 65,000 to 78000#

this last week I had strong side and front winds and the temp went from the mid '70 down to the high 40,s

I don't idle, but I do have an APU but in this weather I rarely run it all night, but use it to keep the batteries charged.

I run around 62 to 65 mostly depending on my schedule, rarely I run over 65, I could go 80 if I wanted.

I drop one gear on most hills, and I will loose 5 to 10 MPH depending on how steep it is.

My rears are 3.65 and I run 22.5 LP tires at the speeds I drive keeps my RPM's at 13 to 14.5 10 speed auto shift by Eaton

I tried slower but engine seems to smother at anything lower than 1200 RPM

you can look at (lejoelle2012) in fuel gauges and see my averages

I do have the cross over pipe blocked so the gases don't go into the intake, I can't say for sure if this is helping or not. It just goes against anything I ever learned about running fast down the quarter mile in my hot rod in the '60's.

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Chad Boblett will be eternally grateful.
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