Question:
Does a tractor use more fuel when bobtailing? I've been told it does - since there is no trailer to provide momentum and intertia,.

Answer:
No way. Much better----10mpg at least. You're 65,000 lbs. lighter. Plus better aerodynamics. Also less tire drag----you have 8 less tires on the pavement.
I do a lot of bob-tailing these days and i keep records.

Answer:
Momentum..........for going down hill.... .
Like mentioned, you'll NOT be using as much fuel since you aren't pulling 60K lbs behind you. You can get up to speed in only a few gears, instead of 15. Thus less fuel being used......etc......

Answer:
Less fuel used during bobtailing.
However, since the truck is really set up for handling weights of up to, or is some cases in excess of, 80,000 lbs, there are other issues when doing a lot of bobtailing such as more difficulty in stopping, it is also harder on the suspension, decreased tire wear and so on.
Answer:
I get about 5-6 mpg with a loaded trailer, 6-7 mpg with an empty trailer.
I get about 11 mpg when bobtailing.
Uturn is right, you can have problems stopping when you're bobtailing.

Answer:
First time bobtailing right out of trucking school, no one told me how hard it would be to stop so I'm hauling (edited) and loving it and then there is a stop sign up the street from where I dropped my trailer off I hit the brakes and I am barely slowing down I'm doing about 50mph and I keep pressing them a little bit harder and harder not much happening the stop sign is coming up quick into a busy intersection so I really lay on the brakes and my (edited) end was shaking hopping and bouncing and the brakes were smoking and I barely stopped in time lets just say it was a lesson learned and my rig gets 12mpg bobtailing 6-7mpg loaded so whoever told you that bobtailing gets less needs to go back to school.

Answer:
If all other conditions are equal, mpg is strictly determined by weight -- how much energy the engine spends to move the truck.
But as posted above -- bobtailing provides some new problems. Braking is the biggest problem in my opinion.
The tractor is designed to carry at least some weight on it's eight rear wheels. Bobtailing without that weight causes the stiff rear suspension, high-pressure tires and over-sensitive brakes to bounce and dance around on the pavement. When bobtailing, the front steer tires carry about 5,000lbs each, while the rear drives oncly carry about 1,000 each. When braking hard, the rear drives simply lock-up and bounce, while the front steers dig into the pavement. This can cause the bobtail to spin-out as the rear end comes around and tries to pass the front.
Bobtailling can be fun. You've got lots of power and the tractor "feels" so manueverable compared to pulling a trailer. But it's not an over-sized SUV, and can easily lose traction if you're not careful. I actually make more following distance when bobtailing, beause I know if I have to brake hard it's going to skid a loooooonnng way before it stops.

Answer:
So if I put "My SUV is bigger than your SUV" on the side of the tractor it might not be the right thing to do?
The longest I ever bobtailed was 980 miles to pick up a trailer. Stopping was always fun but you get adjusted to it. The most fun was all the bouncing. It's not harder on the trucks suspension so much as it is the trucks suspension gets harder. It's made for weight and without it you bump and bounce alot.

Answer:
my longest bob-tail venture was 1,172 miles.
Also remember that the bobtail speed limit in most states is 10-15mph less than the posted speed limit.

Answer:
My tractor is governed at 65 MPH. Bobtailing will get me up there quicker, but I still don't get to go faster. D'oh!

Answer:

Show me where it says that.
I bobtail about 250 miles each week. Pass many HP, DOT cops, County Sheriff Deputies & local cops along the way, all while running the posted speed limit.
Never had a problem or been stopped by any LEO type.
Yes, when bobtailing you SHOULD drive a little slower due to braking ability being less than desired.

Answer:
Driver,
Sounds like to me, that your slack adjusters are out on your truck. Remember, it is important to do a brake pull test on your truck before you hook a trailer. You get a false brake check with the trailer hooked.
Catch you on the flip!

Answer:
Bobtailing the Las Vagas strip is the best. I've been flashed there more than any where else.

Answer:
One thing nobody has mentioned is the steering, youre steering will be a LOT more sensitive without a trailer,just take it easy first few miles to get used to the steering and braking and buckle up its a rough ride![/u]