Fuel Mileage

[ChikinTrucka]

Not sure if it's already been asked or what forum to use, but here it goes...
What fuel mileage are you getting from what truck? Engine? Gears? Trans? Etc?
I drive a 2005 Mack Vision and get between 4.5 and 5.5 MPG, mostly at 1800 RPM +/- and 70 MPH.
I know that really stinks and I'm wondering what truck/engine/trany/rears are the best combo for the best mileage.
Someone recently told me his 2006 Freightshaker gets 6 to 7.5 but he must keep the RPM's at 1650 to do it.
Thanks.

[Double L]

And the driver probably has a Detroit or Mercedes for power and you know how good on fuel they are.

[tracer]

Not sure if it's already been asked or what forum to use, but here it goes...
What fuel mileage are you getting from what truck? Engine? Gears? Trans? Etc?
I drive a 2005 Mack Vision and get between 4.5 and 5.5 MPG, mostly at 1800 RPM +/- and 70 MPH.
I know that really stinks and I'm wondering what truck/engine/trany/rears are the best combo for the best mileage.
Someone recently told me his 2006 Freightshaker gets 6 to 7.5 but he must keep the RPM's at 1650 to do it.
Thanks.

2004 International 9400 with a wind deflector on the roof .. pulling 53" dry van. I have a 475 hp CAT with 1,650 lb/ft torque, 13 speed tranny with 0.73 top gear ratio, and 3.73 rears. I recently switched to low profile tires and I dropped a mile on the speedometer at the same RPM. I get decent fuel mileage (between 6 and 7 mpg) even fully loaded but only because I stay within the engine recommended RPMs. For my CAT, it's 1,300 to 1,400 RPM. I usually do 58 mph with a light load (1,300 rpm) and 60 mph with heavy load in hilly terrain (1,350 rpm).

1,800 rpm sounds too high even for a Mack engine... I'd suggest you found out your engine best RPM range, and maintain the road speed that puts you in that RPMs. You might need to get creative with axle ratios, tires (tall rubber will help you drive faster at better MPG), tranny top gear ratio, etc. But driving outside of your engine favorite "spot" is a sure way to waste tons of dough on diesel.

[klleetrucking]

'03 379 Pete, 475/500 Cat, 18 speed, 355 rrs, flatbed. Coast to coast operation. 6.212 mpg since new. Down to 6.1 since low sulpher.

[allan5oh]

There's so many variables.

Driveline specs are about 20% of the factor.

A more efficient engine doesn't matter if the driver is doing 75 mph.

It's the total package:

- An aerodynamic truck AND trailer
- Low rolling resistance tires(super singles or XDA energy)
- Driven at less then 60 mph
- Eliminate idling
- With good specs for 60 mph(2.64's or 3.55's)

Will net you 7.5-8.5 mpg. That's not a joke.

[bob h]

quote="allan5oh"]There's so many variables.

Driveline specs are about 20% of the factor.

A more efficient engine doesn't matter if the driver is doing 75 mph.

It's the total package:

- An aerodynamic truck AND trailer
- Low rolling resistance tires(super singles or XDA energy)
- Driven at less then 60 mph


*road speed is much less a factor than the resulting engine speed*

- Eliminate idling
- With good specs for 60 mph(2.64's or 3.55's)

Will net you 7.5-8.5 mpg. That's not a joke.[/quote]

[solo379]

[allan5oh]

*road speed is much less a factor than the resulting engine speed*

Are you saying that specs matter more then road speed?

I'd rather have an engine revving 100-200 rpm too high at 60 mph then spot on at 70.

Cummins fuel mileage paper states 4% difference from a perfect spec to a bad one.

Road speed makes many times more difference then that.

If you want to do a test, take a truck with instant read out.

At 60, shift down 2 gears if you have a 13 speed. Notice the difference.

Now speed up to 70 in 13th.

I absolutely guarantee you at 70 you will get much worse fuel mileage.

[bob h]

*road speed is much less a factor than the resulting engine speed*

Are you saying that specs matter more then road speed?

I'd rather have an engine revving 100-200 rpm too high at 60 mph then spot on at 70.

Cummins fuel mileage paper states 4% difference from a perfect spec to a bad one.

Road speed makes many times more difference then that.

If you want to do a test, take a truck with instant read out.

At 60, shift down 2 gears if you have a 13 speed. Notice the difference.

Now speed up to 70 in 13th.

I absolutely guarantee you at 70 you will get much worse fuel mileage.

'As the truck speeds up from 60 to 70 mph', what causes the fuel efficiency to decrease?

I don't believe in the accuracy of your instant readout.

[COLT]

Wind resistance :wink:

[allan5oh]

'As the truck speeds up from 60 to 70 mph', what causes the fuel efficiency to decrease?

I don't believe in the accuracy of your instant readout.

Wind resistance.

It increases exponentially with speed, while road speed increases linearly.

Why don't you trust it? It might be out 2-3 tenths of a MPG. But here's the trick, it will always be out the same amount!

Wind resistance increases 36% from 60 mph to 70 mph.

Proper specs will help, but theres NO substitute for slowing down.

[ChikinTrucka]

'As the truck speeds up from 60 to 70 mph', what causes the fuel efficiency to decrease?

Wind resistance increases 36% from 60 mph to 70 mph.
Proper specs will help, but theres NO substitute for slowing down.

This is the whole reason we had the National speed limit of 55MPH for a while, during the alleged fuel shortage. It is absolutely true, air resistance is a huge factor and the drag increases exponentially with increased speed. Going under 55MPH is even better. But I think most experts will agree, that 60MPH is the breaking point for fuel consumption, so to speak.

[ChikinTrucka]

Thanks for all the great feedback. Mostly what I expected.
So, if YOU were going to buy a new truck, and you had a very tight budget, what would you buy?
Anyone who says Mack gets a time out in the corner!
I pull a flatbed, so I can save some air drag with a lower profile.
I want the 13 speed, or similar, because with the 10 speed, I just loose too much speed between shifts going up hills. And, I'm sure it sucks up the go-juice between shifts when I wind 'er out to 2200 RPM because I know she'll drop to 1300 after I shift and fall on her face. (slight exaggeration, but ya' know wutimean). I don't care about the fancy stuff, I just want to make money. I'm partial to Caterpillar, (probably because I used to run Cat equipment).
This truck sounds pretty good, maybe in a 2008 model:
(does it come in pink?) LOL, Ha ha ha...
2004 International 9400 with a wind deflector on the roof .. pulling 53" dry van. I have a 475 hp CAT with 1,650 lb/ft torque, 13 speed tranny with 0.73 top gear ratio, and 3.73 rears. I recently switched to low profile tires and I dropped a mile on the speedometer at the same RPM. I get decent fuel mileage (between 6 and 7 mpg) even fully loaded but only because I stay within the engine recommended RPMs. For my CAT, it's 1,300 to 1,400 RPM. I usually do 58 mph with a light load (1,300 rpm) and 60 mph with heavy load in hilly terrain (1,350 rpm).

[heavyhaulerss]

i.m.o you cannot beat a det on fuel mileage. at least the 95 i have.

[special k]

You can't beat a detroit for fuel mileage if you're doing lighter work. If you're buying used on a tight budget get a DD that been rebuilt with warranty because the older have a nasty habit of throwing rods through the block with little warning. I'd probably advise a N-14 style Cummins for a good balance between fuel economy and power. CATS are nice but parts are expensive if you get a bad one and the later ones seem hard on fuel. This is assuming your buying a used truck in the 98 and newer era.

[Bandit102]

I'll take the N14 over the Cat or Detroit any day of the year.

I think Detroit did finally remedy that wrist pin bushing problem. But who's to say, if you buy an older one, that the right parts were used. When they turned loose, they sure did ruin a block!

[Wild Bill Pete]

My Pete 359, Cummins 400, 13speed, 2:89 rears, now retired as a living van, used, with flat bed, loaded with low profile loads, to get 7.5 mpg, keeping about 60. Now, with no trailer, 3 ft extension in the frame, and a 26ft low profile box converted to live in, I am getting the best mileage of my truck's life. I once got 10.5 mpg, at 55mph, level ground, no wind, on I10. I usually get about 8.5 - I keep the speed to 60, I am not in a hurry. If I go 70 or higher, even my almost unloaded home goes from 8.5 right down to 5. Current constant weight is 28950.

[ChikinTrucka]

That sounds cool, Wild Bill.
That brings up another question.
How much difference should one expect between flatbed v. Van?
I'm told that flatbeds typically get worse fuel mileage because the tarps really 'grab' the air. But it sounds like you did OK.

[ChikinTrucka]

I just noticed something here.
"Route selection: Interstate v. congested road= 20%"

I typically get routed over the SHORTEST route, which is typically the most traffic and most big steep hills. I prefer to take the longer, less traffic route and if possible, flatter.
For you guys who run the Northeast, here's a typical example:
I-95 from New Hampshire to I-495 to I-290 to I-90 to I-84 to I-91 to I-95 to NYC (George Washington Bridge) to I-287 to I-78 to I-81 and on South.
or
I-95 from New Hampshire to I-495 to I-290 to I-90 to I-84 to I-81 (in Scranton, PA) and South.
The latter is 25 miles longer, but typically saves me 2 to 5 hours of traffic jambs.
The 'company' wants me to take the 'shorter' route and sit in traffic.
How much is too much, and at what point do the miles cost more than the traffic? Judging from this example, I'd guess I could go up to 20% more miles without burning more fuel.

[solo379]

Judging from this example, I'd guess I could go up to 20% more miles without burning more fuel.[/color]

Yes. But don't forget, it's "up to 20%",so, it could be less, and it applies only on congested portion.
And another thing;- miles not only burn fuel...
So it's individual decision, and should be taken on case to case basis! :wink: 8)