MonacoRon
Nawth AlaBamma
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Joined: 11/20/2003
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My Dynasty shifts into 6th when the speedo indicates 60MPH and is not under a strain (uphill, accelerating, etc). I know that each 5mph increase in speed will lead to a slight increase in fuel consumption. So, what's better, driving 55mph in 5th or 60 mph in 6th? I figure each engine/tranny configuration and coach design will be slightly different, but in general terms, what do you think will give the best fuel efficiency?
Nawth AlaBamma
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Polishnurse
Schodack, NY
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Joined: 03/13/2007
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I'd have to say the 6th gear, at 60 is the optimal. Not all vechicales are designed to run 55. I just won't push it to maintain the 60 MPH. I run a gasser and find 62 is perhaps the grove it likes on the flat. JM2Cents Bill
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AMW1721
Douglasville, GA
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Joined: 07/06/2005
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Driving 60-65 will give you the best mpg.Your tran will stay in 6th geer and not flip back and fowered to 6th.
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rv2go
Somewhere between Knoxville, TN and the coast.
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Joined: 12/26/2000
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My Allison shifts into 6th at about 54mph. If I want to drive at 55mph, I will use the "eco" setting on the transmission shifter. Go until it shifts into 6th, then set the cruise on 55. In the "eco" mode, the trany will not downshift as fast. The speed will go down to 50 or less before it will downshift to 5th.
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GRice
Alsip,IL
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Joined: 11/01/2002
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I've been using rpm to help out some with mileage, 6th gear in economy mode with our Allison at 1700 rpms I can cruise at or just a tad above 60mph, which keeps me going good with traffic.
Gary & Susan R
2005 Alfa See-Ya Founder
2005 Chevy Avalanche
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zmotorsports
Utah
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Joined: 11/29/2007
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The highest gear with the lowest RPM will usually net the best economy. I would either use the 'economy mode' on the selector or add a little RPM to that so the trans doesn't hunt back and forth between fifth and sixth. Mike.
Mike & Chrystal (F315002)
2003 Monaco Dynasty/ 26' Haulmark Edge trailer
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Jayco-noslide
Galesburg,Il., USA
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In allmost every case, I would say the slower the better but your's seems to be an exception because of the 6th gear situation so 60 in 6th is probably best for MPG.
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KOG
Winterville GA
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Joined: 01/31/2001
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Here's another idea. Try running it at both speeds and see what it does. If you can keep in in 6th at 55, fine. If not it may actually do better in 5th at 55 than in 6th at 60. You really won't know until you've tried it. If it were a gas engine there would be no question. 6th gear would be better. Diesels aren't the same animal.
I can tell you that there will be VERY little difference either way and if it were me I'd be running it at 60-65 in 6th.
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Deen
Vancouver, WA
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Joined: 12/07/2000
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GRice wrote:I've been using rpm to help out some with mileage, 6th gear in economy mode with our Allison at 1700 rpms I can cruise at or just a tad above 60mph, which keeps me going good with traffic. At 60 mph in 6th I'm turning just about 1,550, my torque peak is 1400 to just past 1700 (due to the Banks kit). Set the cruise at 60, punch the "economy" mode button and enjoy the ride. If I try to run 55 it downshifts at every little hill so 60 works for me.
Deen - Vancouver, WA
'02 Dutch Star 4090 (41+', triple slide)
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chuck4788
West of the Middle
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I think slower is better.
I ran a test using the Silverleaf to display engine fuel consumption data while using 5th and 6th gears at 55 and 60mph. The differnces between 5th and 6th were slight, the difference between 55 and 60mph were much greater and for me confirms the data in the Cat RV Performance Guide.
The Cat guide shows a 40,000 pound MH requires 110 road HP for 55mph, 134hp for 60mph and 182HP for 65mph.
My MH has an Allison 4000 transmission and 60mph in 6th is 1338rpm and 55mph in 5th is 1438 rpm, a difference of 80rpm. I don't think this small a change in engine speed alters the efficiency of the engine enough to offset the better milleage at 55mph.
Chuck
02 Beaver
505hp C12 Cat
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