Fuel economy at 65 mph vs 60 mph

Cummins12V98 wrote:

Oldelevatorman wrote:
Ok can somebody give me a good reason why you would tow a trailer at 70 mph? Doesn't seem safe or smart.

If you are on a remote area where the speed limit allows and you have a TV that can handle your RV and all tires are rated for that speed there is no problem doing so.

I normally tow at 60 but when I want to get out of cold windy weather I will ramp it up a bit and pay the price in MUCH lower fuel mileage!

Ron looks like you are in a hurry to get to a fuel station before it hits empty. yes I would tease you if you were face to face visiting.

chevman

Oldelevatorman wrote:
Ok can somebody give me a good reason why you would tow a trailer at 70 mph? Doesn't seem safe or smart.

If you are on a remote area where the speed limit allows and you have a TV that can handle your RV and all tires are rated for that speed there is no problem doing so.

I normally tow at 60 but when I want to get out of cold windy weather I will ramp it up a bit and pay the price in MUCH lower fuel mileage!

Ok can somebody give me a good reason why you would tow a trailer at 70 mph? Doesn't seem safe or smart.

ACZL wrote:
You're pushing the same amount of air out of the way at 60 mph as you are at 70 mph.

Not true from a physics standpoint. When you double your speed, you encounter four times the wind resistance, and you need eight times the horsepower to maintain that speed.

Posted: 04/21/15 09:38am Link | Quote | Edit | Print | Notify Moderator

We just completed a holiday run from Toronto, Cnd to Kissimmee, Fl.
Some of stats from this trip.

TV: 2014 Ford F250 Super Duty, 6.3 gas, 4.30 ratio, 6 spd.
Coach: 2014 Cougar 327 RES, (Mfg. spec's 10,260 lbs., 1,625 lbs. pin)
Have yet to put it on a scale but could likely add 1,700 lbs. for gear and 1/4 tank of fresh water.

US 90, 79, 19, 77, 95, 4.
Return trip: 2,806.7 miles
Moving time: 56.28 hrs
Moving average 50 mph
I tried to hold the speed at 62 - 63 mph and tried to keep the RPM from going above 3,000. This meant slower hill speeds.

South bound April 2,3 & 4th, 2015
Used speed control when not on wet roads.
6.6 mpg (we had heavy rain)
172.141 US gallons, Average $pg $2.27,

North bound April 16,17 & 18th, 2015
Used manual gas pedal especially in mountains to keep the RPM in check.
6.9 mpg
172.338 US gallons, Average $pg $2.38
Tried to fuel at Flying J and Pilot's to take advantage of the Good Sam discount and larger rig friendly fueling stations.

NOTE: we did get up to 9.047 mpg in the Southern state flat lands, but the Blue Ridge, Appalachian , Allegheny mountain ranges brought us down to 6-7 mpg area.

YEP... we did see those diesel dually's through Fancy Gap passing us, but for our use the cost/benefit still supports a single axle gaser.
Coach pulled extremely well... very much appreciated especially after some of those longer days behind the wheel. (single driver)

Nice trip, fuel consumption was at the lower end of our expectation but no big surprise.

Happy trails!!!!
GPG

mtofell1 wrote:

larry barnhart wrote:
Before our 05 truck had a speedometer issue the dash showed the correct fuel mileage and fuel used.

I had this in my 06 and REALLY miss it in my new truck. It was super nice to know how much fuel I had left instead of just finding a station when the dummy light comes on. My Ram is supposed to have a 32 gallon tank but the light comes on after about 25 gallons have been used :h

We have an inbed fuel tank so we can buy when we want and not when we need. After the speedometer was fixed in 09 it is still close enough like under 2 gallons used from the fill up.

chevman

larry barnhart wrote:
Before our 05 truck had a speedometer issue the dash showed the correct fuel mileage and fuel used.

I had this in my 06 and REALLY miss it in my new truck. It was super nice to know how much fuel I had left instead of just finding a station when the dummy light comes on. My Ram is supposed to have a 32 gallon tank but the light comes on after about 25 gallons have been used :h

Before our 05 truck had a speedometer issue the dash showed the correct fuel mileage and fuel used. Same as the fill up and same as the math. I noticed the mpg started to climb after we hit 60 mph. 55 as in Oregon showed this to us several times. I decided to speed to 60 and proved it. Several times so I kinda proved it to me. 65 mph was not the better just over 60.

chevman

ACZL wrote:
You're pushing the same amount of air out of the way at 60 mph as you are at 70 mph. Technically, like others have said, going slower will net a bit better mpg's, but overall with today's engines (specifically diesels), they are designed to be most efficient around 65-70 mph.

Completely disagree.

It's easy to see where your mileage is best by towing on flat ground and looking at your instant average MPG. Towing at 55-65 will net much better mileage than 65-70.

It takes more fuel the faster you tow. Simple as that.

You're pushing the same amount of air out of the way at 60 mph as you are at 70 mph. Technically, like others have said, going slower will net a bit better mpg's, but overall with today's engines (specifically diesels), they are designed to be most efficient around 65-70 mph.