Does speeding save fuel?

When I was running to the West Coast my average was below 6.5 mpg. When stayed in the Midwest the last 2 years, it jumped up to 7.5. The weights and speed at which I drive has not changed too much (keeping in the range of 65 - 70 mph - rarely went over 70mph in the West anyway) but the terrain and less head winds made the difference.

 

I think it's possible to have engines on a SST type plane now that you can have a output of sufficient power to stay beyond supersonic without the use of burners. The Concorde is quite the monster in it's day. We explored using one and it at that time was in the realm of 3000 dollars a man for USA from London, and there was 4 of us. I think it was close to 2000 on the speedbird (British Airways) via L-1011 and Bermuda to get back. I would be happy never to ride a L-1011 again because those engines were the so called whisper jet on emissions and noise control. You could hardly get it off the ground and fight to cruise. We used all of the runway 110 at KBWI which is a little more than two miles if I remember right to get to and stay at speed to fly. I think the weight involved was around 430-460 thousands of pounds depending on which model at full TO weight.

As far as trucking, engines were able to "Breathe" quite a bit and have a wonderful range of RPM if you could get all of it. A couple Macks I could get to 3200 RPM which is outrageous at the time (In those days 2300 was common) thanks to a fuel pump that kept giving.

Today's trucks are lucky to operate in say 1250 to 1600 or so. It's not much room to work with. You could go higher but horsies go away quick as does the torque. I am not getting into all the computer hocus pocus that is possible.

Fuel mileage has gone up, we turned in anywhere from 6.5 to 7 and change average per trip. 63 was not ideal for us, but you use what you are given. I function better between 72 and 85. They started turning down trucks back in the 90's and then adding on additional enforcement type tools when possible as it evolved from there.

And you still have accidents. *Shrugs.

 

Yea we'll always have an argument for going faster, just like the slow ones will always have an argument for going slow. The first time that going 5 over gets you to your unload and reload with 5 minutes left before they close and you're waiting till tomorrow morning to load instead of being an hour or two down the road, you'll understand.

 

I think so.

My Company 12.7 preemission Detroit is happy right at 68 mph turning 1500 fully loaded at 80,000.

Tried slowing down to 63 to meet my companies requirement for a penny a mile speed bonus.

Truck don't like that speed with the 10 speed.

Any little Grade slows the truck down , soon dropping me into the 50s and having to make a huge jump down to 9th.

Cruise set at 68 motor turning 1500. Any upcoming grade I bury the pedal and build some boost before the ascent starts.

Truck never drops below 1300 with no need to drop gears every other slight grade.

Now if the truck was speced differently it might be another story.

My new used truck I bought has the Cummins Select n-14 with a 13 speed.

It was turning 1600 right at 70 in 13 th on the test drive.
Looking forward to being able to Split that top gear.

 

The more rpm the more fuel it uses. Many new motors are built with more toque. My Volvo will climb Monteagle at 59 with 35k on. Never kicks down to a higher rpm. Just stays at 1250. I'm getting 7.5 now. They did a software upgrade.

 

More rpm equals more fuel burned? They really should've figured out how to get a big cam to run at 1350 instead of 1800 the new stuff wouldn't get close to touching their mileage. If your engine is designed to run lower rpms then yes you use more at higher rpm, a high revving motor will self destruct you try dragging it down like that. The old big cams would do 6 mile a gallon with a good driver in them and I'd bet your truck doesn't even see the bottom end of their operating range.

 

If you own your own and buy tires etc, you save on all items in the long run. Trans, rears, tires run hotter when hammer down. But you add $$ to the oil companies and the fuel tax coffers.

 

Your correct. But is that a common occurrence? Everyone has a hurry situation once in awhile. If you needed a good used truck..would you want one thats been held to the floor all its life..or one thats been run easier?

 

If you got 6mpg with the old ntc big cam, either you were hauling feathered pillows, or bob tailing. I have run them over 1million miles back when I had a 290 and then 350s never got that high mpg. But mayby you or someone you know has a special driving skill. When I purchased a 60 series 11.1 doing same runs got high 6s to 7mpg.

 

Happens to me a couple times a week usually, if I ran strictly speed limit I'd lose out on 600 bucks a week pretty easy, or never be home because I've gotta sit 500 miles away all weekend.