Speed vs. "sweet spot"

[mbozz282]

With my Truck I tried it, and it did not matter what speed I went, I got the same bad fuel milage, 5.56. 55mph or 75mph. So I said why be a road hazard and go with the flow.

Im with you i dont know why but i average 5.3 to5.6 no matter what speed or weight in flats or mountains.

[solo379]

but not 'most' effect.

So, what does? Are you want to say, that going 75mph into 30mph cross wind, you'll get the same mileage, as going 60mph in the same wind, with the same load? Why don't you try to compare apples to apples?
And about "550hp+ fuel guzzlers"...It's not what you got, it's how you use it.

[heavyhaulerss]

Im with you i dont know why but i average 5.3 to5.6 no matter what speed or weight in flats or mountains.

same m.p.g. at any speed, terrain, & weight? this is a first I have heard of such results. I have definitely never experience this myself.

[Barney the Cabover]

With my Truck I tried it, and it did not matter what speed I went, I got the same bad fuel milage, 5.56. 55mph or 75mph. So I said why be a road hazard and go with the flow.

Think whatever you want to ding dong. I've been driving 57 for over 3 years and I have at least 4 other friends who have been doing it for 2 or more years. At least 1,000,000mi of personal experience and not one of us have had an accident.

If your truck gets horrible (and anything under 6.5 mpg I consider horrible) fuel mileage no matter what speed you drive, there is something mechanically wrong with it and you should get it fixed.

Laugh and shake your head all you want. I used to have a "cool" truck that averaged 5.17 mpg for the entire year. I've made $10,000 more in 10 months of this year then I did the whole last year with my "cool" truck driving 70. I've done that in 106,000 miles, home every weekend and occasionally during the week.

[eplurubus]

So, what does?

I don't know. I think there's too many variables to say that one single, definite thing has the 'most' effect. But if one says that speed accounts for 5% of the pie, and other variables each count for 4.9% and less, then it would be the 'most'. I just don't think it is. I think it changes constantly.

Are you want to say, that going 75mph into 30mph cross wind, you'll get the same mileage, as going 60mph in the same wind, with the same load

When I encounter 30mph sustained crosswinds (which usually come with higher gusts) while I'm empty, I will drop my speed considerably and I still get 4.5mpg, just the same as if I drove 75. I know that because I'll do 75 in a big crosswind when I'm loaded and guess what: I get 4.5

[Bulldog]

The only way that I could say that speed would play such a significant role in your fuel mileage, would be if you were a dedicated run kind of guy. Because things change so much over the course of the day, it would be hard to say that it plays such a high percentage of your fuel consumption. To each his own though.

[allan5oh]

It has the most effect? How much more effect does it have than weights upwards of one-hundred thousand pounds? How much more effect does it have than 550hp+ fuel guzzlers? How much more effect does it have than hefty crosswinds or headwinds? I could keep going with the questions, but I'll stop there and agree that speed has 'some' effect, but not 'most' effect.

I was speaking of driver behaviour. Out of "sweet spot", accelerating from a stop, idling etc... the speed he chooses to drive at has the largest effect.

When you have a stiff side wind, the speed chosen to cruise at becomes even more important.

[coastie]

Think whatever you want to ding dong. I've been driving 57 for over 3 years and I have at least 4 other friends who have been doing it for 2 or more years. At least 1,000,000mi of personal experience and not one of us have had an accident.

If your truck gets horrible (and anything under 6.5 mpg I consider horrible) fuel mileage no matter what speed you drive, there is something mechanically wrong with it and you should get it fixed.

Laugh and shake your head all you want. I used to have a "cool" truck that averaged 5.17 mpg for the entire year. I've made $10,000 more in 10 months of this year then I did the whole last year with my "cool" truck driving 70. I've done that in 106,000 miles, home every weekend and occasionally during the week.

I never said 5.56mpg was good, and I have been seeking ways to increase it. But shake your head all you want the results I am getting is what I AM GETTING. But I refuse tyo be an ROAD HAZARD by going slower than the flow of traffic. That is Dangerous and one reason I got my own Truck so I would not be a danger on the Highway. Going Slower is not safer, but causes a DANGER.

[allan5oh]

I go 60 mph all the time, how is that a danger?

[firebird_1252]

i've been thinking about this thread alot the past few days.

maybe my theory about how you take off and where you shift is motor.


as i said before my s60 gets great milage short shifting..

while my truck was down i had a columbia with a acert c15.. 5.86 mpg... ran 70 @1500 rpm i short shifted it and babied the hell out of it.. oh and it was a 410 hp motor.

[heavyhaulerss]

i've been thinking about this thread alot the past few days.

maybe my theory about how you take off and where you shift is motor.


as i said before my s60 gets great milage short shifting..

while my truck was down i had a columbia with a acert c15.. 5.86 mpg... ran 70 @1500 rpm i short shifted it and babied the hell out of it.. oh and it was a 410 hp motor.

what exactly do u mean short shifting? shifting at a lower r.p.m. ?

[Heavy Duty]

I go 60 mph all the time, how is that a danger?

Now I know who that was flying thru the TS parking lot.

[firebird_1252]

what exactly do u mean short shifting? shifting at a lower r.p.m. ?

yes under 1500rpm

[LBF]

short shifting, or progressive shifting, is about grabbing the next gear at the lowest possible revs. In the lower gears, you are shifting up from idle through 5 or so, at 1000 increasing to 1500 or so, in steps, as low as it will still pull in the next gear. As you get to the mid and higher gears, you have to spin it a little faster, since those gears won't pull too well from way down.

Figure, the goal is the fewest number of ups and downs of the pistons to get you up to speed. Spinning the engine to 1500 and beyond in the lowest gears isn't needed and just wastes fuel.

money in your pocket or up the stacks, your choice.

Need a YouTube video to demonstrate the technique

[solo379]

When I encounter 30mph sustained crosswinds (which usually come with higher gusts) while I'm empty, I will drop my speed considerably and I still get 4.5mpg, just the same as if I drove 75. I know that because I'll do 75 in a big crosswind when I'm loaded and guess what: I get 4.5

You must be driving in some twilight zone, that defies the laws of physics....

[tracer]

Same here. I get 4.5 whether I do 55, 65 or 75. So, guess which one I'm gonna go with (hint: it's not 55 or 65).

i looked over my dyno tuning result sheet where they mapped the current horse power and rpm. using the torque vs horse power formula, i was able to calculate how much torque exactly my engine makes at each rpm. here's the results:

rpm hp torque
1200 450 1969
1300 475 1919
1325 481 1906
1350 490 1906
1375 500 1909
1400 510 1913
1425 520 1916

so the highest torque is at 1200 rpm as it should be and then it goes down at 1325 and 1350 rpm, and starts rising slightly again at 1375. the dyno guy said, "drive at 1375 rpm minimum when loaded" but the above numbers don't prove that's true, as at 1300 rpm i have more torque than at 1375 rpm!

with my 512 rpm tires, 3.73 axles and 0.73 13 speed, i do 56 mph at 1300, 57 mph at 1325 and 60 mph at 1394 rpm. i'm driving from alberta back to civilization on 11/17 tomorrow and will try driving at the superslow 56 mph. my load is about 30,000 lbs. i drove at 58 mph (1347 rpm) today from regina, sk and due to harsh weather and winds, my fuel mileage was worse than usual

i have a digital tachometer in my gearmaster and the difference is about 50 rpm between that and the analog one on the dash.

this is a very interesting discussion as i've been thinking of changing my axle ratio to 3.58 or even 3.42 to be able to run a bit faster, but maybe super-slow speed is the answer? btw, the speed limit on 11/17 in northern ontario is 90 km/h (56 mph) which is perfect for my little experiment. will publish results in my blog on the trip completion.

[Fredog]

I used to have a "cool" truck that averaged 5.17 mpg for the entire year.


why didnt you get it fixed?