m1e9r5c6
Igloo#4, Canada, eh?
Full Member
Joined: 02/10/2010
View Profile
 Offline
|
As said previously, your gain may differ depending on your combination but in general yes you will see a significant gain.
FYI, my 04 ram cummins with 6spd manual eats fuel if rpm goes to 2000 or above. If I keep it under that, 65mph or below, I get significant savings. Usually an added 5mpg or more.
2004 Keystone Laredo 29GS
2000 Invader Mirage 170, 115hp o/b
2004.5 Dodge Ram 2500 SLT, QCLB, 5.9L CTD, 6 spd manual
|
JustLabs
Washington State
Senior Member
Joined: 05/13/2002
View Profile
Offline
|
Going from 55-70mph wind drag is doubled. Its an exponential increase,not linear. Wind drag increases in a hurry.
I've also read that wind drag decreases fuel economy by 2% for every mph over 55 that you drive.
2011 Chevrolet 2500HD LTZ 4x4 CCLB Duramax/Allison
2007 Keystone Cougar 289BHS Fifth Wheel.
|
Jayco-noslide
Galesburg,Il., USA
Senior Member
Joined: 11/24/2004
View Profile
Offline
|
No matter what you are driving with very few exceptions, MPG is always going to go down with speed. It's pretty much basic physics; that is, it takes more energy to move a given weight faster. Also, the wind resistance of what you are towing goes up rapidly with more speed. The only exception would be if you slow down to the extent that the trans shifts into a lower gear causing an increase in engine RPM's but that isn't going to happen probably unless you get below 50. Don't buy it when people tell you that their engine has a certain "sweet spot" where it gets it's best MPG at a higher speed. Your word "noticeable" might be important as a small decrease in speed might not be noticeable but it's still going to occur. I bet if you slowed to 55-58 MPH you would see a 2 to 4 MPG increase.
Jayco-noslide
|
laknox
Arizona
Senior Member
Joined: 01/06/2008
View Profile
Good Sam RV Club Member
Offline
|
amxpress wrote:Yes, you will see a difference in MPG if you cruise at 60-65 vs 70.
I see a difference when going 60 vs 65 with mine.
BTW, if you have factory ST tires on your Sandpiper, they have a speed rating of 65 mph.
x2 on both speed and tires. I figure about +1-1.5 mpg at 60 vs 65 on my setup.
Lyle
2002 GMC Sierra 2500 HD Duramax Crew Cab 4x4
Banks Bullet Tuner and Monster Exhaust
B&W Turnover Ball with 5th Wheel Companion
2004 Komfort 25FSG Fifth Wheel
1936 John Deere Model A
International Flying Farmers 55 Year Member
|
Francesca Knowles
Port Hadlock, Washington
Senior Member
Joined: 02/23/2011
View Profile
 Online
|
There's an interesting fuel use calculator at MPG for Speed
Not towing-specific but the proportional savings are striking to look at...
Here are the results for a car averaging 22 mpg/highway at 55 mph.
Speed....time....MPG
55 MPH- 33 min.- 22.0
60 MPH- 30 min.- 21.3
65 MPH- 28 min.- 20.2
70 MPH- 26 min.- 18.3
75 MPH- 24 min.- 16.9
80 MPH- 23 min.- 15.8
" Not every mind that wanders is lost. " With apologies to J.R.R. Tolkien
|
|
|
valhalla360
No paticular place.
Senior Member
Joined: 08/19/2009
View Profile
|
bfast54 wrote:Yes, unless you are heading into a Strong headwind..............then all bets off.
You are pulling a BIG SAIL into the wind, the faster you try to pull it, the more fuel you will consume..................and it will be more work on the truck, and fray your nerves.
It's even more important in a strong headwind. In terms of drag, a headwind is the same as going that much faster. Sailors use the term apparent wind where you combine the effects of the true wind and the speed of the vehicle to get the wind that the vehicle feels.
We get just shy of 13mpg doing 55-60mph normally. Last fall we did a short run into a 30mph head wind and were only doing 50mph. We only got 9mpg. Of course the drag was equivilent to doing 80mph (50mph +30mph). The next day we were cruising at 60mph and got a 20mph tail wind and got 16mpg.
Around 40-50mph (apparent wind), there is a break even point. Below that speed, internal drivetrain friction uses most of the power. Above that speed, air drag uses up most of the power. Optimial fuel efficency on level ground with no wind is typically around 45mph assuming your truck can stay in overdrive.
Tammy Mike & the Bilge Rat (AKA: Diego)
Ford F250 7.3L
1997 Sunnybrook 27' 5er
1995 Gemini Sail Catamaran 34'
Full Time spliting time between boat and 5er
|
tjar66
Camarillo CA
Senior Member
Joined: 03/09/2004
View Profile
Offline
|
My milage drop significantly the faster I go, empty or loaded. 60-65 is my sweet spot with 3.73 gears.
2006 Dodge Ram 3500 Cummins
2007 Desert Fox 305j
2004 TRX 450r Mine
2005 Yamaha Raptor 350 Wife's
2006 Honda 300ex Sons
2007 Honda 250ex Daughter
|
gmg
Houston, TX, USA
Full Member
Joined: 11/14/2004
View Profile
Offline
|
Have you noticed how many truckers have slowed down from 70 to between 55 and 62? The reason is because they save thousands of dollars per year by slowing down. It only makes sense when fuel prices are so high. You may also notice this is mostly for owner/operators. company drivers often still hammer down as fast they can get away with. For me it takes a real effort not to drive 70 or 75 but I am really trying. I am managing to hold it to about 62 average and yes at the end of the day, I am not as fatigued. That extra 10 mph is the most expensive mph you can drive. By the way, my last speeding tickett helped make a believer of me also.
GG, 03 Silverado 2500 Crew Cab DA; Pullrite Superglide Hitch; 05 Everest 294L 5th Wheel.
|
Francesca Knowles
Port Hadlock, Washington
Senior Member
Joined: 02/23/2011
View Profile
Online
|
gmg wrote:Have you noticed how many truckers have slowed down from 70 to between 55 and 62? The reason is because they save thousands of dollars per year by slowing down. It only makes sense when fuel prices are so high. You may also notice this is mostly for owner/operators. company drivers often still hammer down as fast they can get away with. For me it takes a real effort not to drive 70 or 75 but I am really trying. I am managing to hold it to about 62 average and yes at the end of the day, I am not as fatigued. That extra 10 mph is the most expensive mph you can drive. By the way, my last speeding tickett helped make a believer of me also.
And it isn't just truckers!
Even the airlines are getting the message.
The following quote is from the New York Times
"A number of airlines are flying their planes somewhat slower in order to save fuel — 480 miles an hour, for example, instead of the usual cruising speed of 500 m.p.h."
|
Turtle n Peeps
California
Senior Member
Joined: 06/23/2008
View Profile
Offline
|
As speed is doubled HP is cubed.
It takes 4 time the HP to go from 30 MPH to 60 MPH. That is a bunch. 
~ Too many freaks & not enough circuses ~
"Life is not tried ~ it is merely survived ~ if you're standing
outside the fire"
|
|
|
