ISX vs C15 fuel economy (and 379vsW900)

[Camstyn]

I just bid on a contract that needs two tractors/trailers, 5000 miles per week combined. I played it safe and figured on getting 4.6mpg, but I think 5.5+ is easily achievable. Fuel economy is going to make me or break me on this one, so engine choice is my biggest dilemna. I don't really have a preference here so I'd like to hear some unbiased info to help me order my trucks. Here's the details:

two Pete 379-127's, 70" shack, 244" wb, pulling 53' tandem axle dry vans, loads will be light.
I was planning on roadranger 18spd's in both, but the guy I spoke with at Volvo told me that the ZF automated trannies are getting an average of .5mpg better than the manuals. I don't know if I should believe him or not, but if that's true then I'll go that route, it will save me a lot of money every month.

Terrain is very hilly, speed limits are almost exclusively 55-65mph. I'll be piloting one of them and I'll have a driver in the other one, and both of these trucks will be driven with fuel economy in mind (or else!).


My brother's 2004 KW W9 has the 475hp C15 pulling tandem axle ****** in 48 states and says that he gets about 5.8mpg (keeping it below 1400rpm) if he's not being ******* it.. That's with an auto tranny, less hilly terrain than I'll be in, but pulling heavier loads than what I will have. Is the cummins capable of doing the same or better?

I haven't ordered trucks yet so I still have the opportunity to go with KW W9's instead but this has nothing to do with fuel economy.. But if anyone who has driven both can give me their objective opinion on how they compare I'd appreciate that too.

Thanks in advance!

Cam

 

[apextrans]

Cam,

I dont know about the ISX, but I have a C-15 ACERT 550 (started out as a 475) that to date, has never broken the 5.0 MPG. I'm getting LOW 4's & sometimes high 3's. I pull heavy loads on pretty flat terrian, but I drive it hard & high into the RPM range. I've got an Eaton fuller 13 behind it. The Cat rep told me to change my driving style & lug the motor into the 14 - 15 hundred range on the tach & it will run right. ******** If I ran it that low the truck would stall on the climb, mild as it may be. I learned from another member here ( PackRat) that a muffler change could net almost another mile per gallon & increase power. I swapped out the catalytic mufflers to baffled mufflers over the holiday weekend but haven't had a run to test them out yet. If you're running hill terrian w/an 18speed, I doubt you would be able to keep the truck in the 1400 RPM range. I would figure on 1700-1900 & about 3.8 - 4.1 mpg. JMO but I would look for something used & stay away from these new emmission motors...if fuel mileage is your concern. I had a VNL Volvo with detriot in it that consistently got 5.8 or better no matter how I drove it. Hope this helps & good luck with the contract

 

[Camstyn]

Thanks for the advice. I hate the idea of owning one of these new emissions engines but the contract specifies for two brand new trucks and trailers. I looked at a Volvo VN780 and they only offer the ISX or Volvo engines, the only way to get a detroit now is in a western star or freightliner.

 

[Deezle1]

A Western Star is a handsome truck.....but why not go with a Peterbuilt and get almost any engine tranny set up you want, not to mention the petes look great:drool:

Or you could get a newer mack i cant help it...i love me a mack truck, ask anyone

Dom

 

[maniac]

My 600Hp Cat is consistent 5.6 always has, pull a tanker so don't have too much wind resistance, plus I drive it balls to the wall.

Apextrans, i tried the lug down routine and the 2050 lbb of tourque chewed up the rear, ALL the teeth off the ring gear, didn't do anything for the fuel mileage either.

The rebuilder took one look and said "big Cat huh?"

Also Apex, I'm not sure of this BUT taking off the catalytic converters is "tampering" with emissions equiptment in a 4-wheeler, don't know if it applies to trucks or not, don't want to find out either.

Cam, from what I hear the EGR motors, (Cummins and Detroit) are NOT doing well in the fuel mileage dept.

I hear 2 diferent stories about the Cat Accert, some guys say lousy, some guys say great.

I believe it's all in the left foot myself

 

[apextrans]

Well, if it calls for new trucks & trailers, emmission motors are all you can do I guess. Dom's on the money. Peterbilt offers the widest choice of motor options. Sky's the limit.

Maniac, lugging didn't work for me either. MPG was a little better, but not worth the lost time running slower. I drive mine full tilt too. I talked to both a CAT & Peterbilt rep who told me changing the mufflers will NOT void any warrenties, but is illegal (tampering), & if DOT catches it, there WILL be stiff fines. But there aren't to many DOT guys that I've come across who look behind the muffler covers. In addition, the mufflers I put on are almost identical to the catalytic mufflers I took off. The only difference I could find was a small tab welded to the top of the old mufflers. I think it may have been a hanger as it came down the assembly line or something. Anyway, as lousy as this thing runs, I'm willing to take the risk for another 175-200 miles out of a fill up & more power. It is hit or miss with these new motors. My buddy has an ACERT that's two weeks newer than mine & that truck is a freakin' missle Mine must have been built on a Friday

 

[Pacific]

With the price of fuel here in B.C. better get a truck with the best fuel mileage you can get. Who are you pulling van for ?

I see your going with max wheelbase with 53s I hope you are not planning on pulling through the older parts of Vancouver you maybe running over some english as second language drivers

I know two guys with Petes with C-15s in the 500hp range they both said their mpg isn't that good.

You should spec the trucks light as you can but still run 12 and super 40s to survive the hills we have here in B.C.

Good luck with the truck choice

 

[maniac]

Yeah I agree Apex, gotta do what ya gotta do.

Cam, after thinking on this awhile, if fuel mileage can make or break this I don't think it's worth it, especially with 2 new truck payments and a hired driver.

Fuel costs are your most unreliable estimate in this buisness, and "variable" sometimes can't even describe them.

Did you build in a fuel surcharge? One that is variable?

Mine changes EVERY Monday, and is based on average price here in the northeast.

It is right a 12% this week.

 

[Camstyn]

Pacific, my point to point is W. Georgia St. to Cranbrook hauling for Canada Post. Do you think I'll have trouble getting in/out of the city with this wheelbase? I was planning on ordering the trailers with the axles all the way back too for better weight placement. My arrival/departure times in Vancouver are 1-2pm and 4-6am so I don't think the streets will be too congested at those times of day, I'll be using the georgia viaduct.

I know Detroits were mileage kings pre-emissions, I have no idea what works best anymore though. I'm not a Freightliner fan so if I ended up going with Detroits they would definitely be going into Western Stars.

I'm not sold on the MB 4000 series or the Volvo VED-12, as a matter of fact I was surprised when the Volvo salesman told me straight up that the VED-12 gets no better mileage than the ISX.

I'm starting to lean towards the C15, sounds like it has more potential to get good fuel mileage than an EGR engine. A section of straight pipe welded through the inside of the catalyst mufflers sounds like a good idea to me!

maniac you're dead on with the fuel mileage summary. It's of the utmost importance, the difference for me between 4.6mpg and 5.8mpg is almost $4000 per month. At least I'll get all of my GST back from it. Canada Post has a fuel subsidy program going on, I currently get a check every three months, my last one covered 22% of my fuel cost but I'm not sure how they calculate it.. But when I started the 5yr contract that I'm on now, 3yrs ago, fuel prices were only about 63% of what they are at now.

 

[apextrans]

A section of straight pipe welded through the inside of the catalyst mufflers sounds like a good idea to me!

No can do partner. The catalyst is some kind of liquid as opposed to the honeycomb variety. The CAT rep told me NOT to punch thru them unless I wanted a HUGE mess to clean up & it's pretty nasty stuff apparently. I looked down thru my old ones & couldn't see out the other end. I got part #'s for no catalytic mufflers when you want them. You can get Detriots in Peterbilts too. I don't know what a Western Star runs up there, but big $$$$ down here.

 

[Camstyn]

Are you sure you can get a Detroit in a Pete? I was under the impression that they are only available in Daimler trucks.

I hate the idea of a Paccar truck with anything but a Cat or Cummins in it, but if it saves fuel I think I could stomach it, as long as the fuel savings work out to be more than the hit the truck would take for resale value.

 

[maniac]

Canada Post has a fuel subsidy program going on, I currently get a check every three months, my last one covered 22% of my fuel cost

HMMM.

Last year average price per gallon I paid was 1.69
My average cost was 96 Cents after the surcharge.

So far this year my average price paid is 2.14
and cost is 1.11 I suspect it will not get any better.
Last year the price was in the 2 dollar range only part of the year, this year it will be up there all year if not nearing 2.50.

With the way fuel prices are I won't be replacing my truck any time soon, most of our guys feel pretty much the same way. And from what I hear the 07's will be about 10% higher

 

[Camstyn]

Yes apparently they've already started charging for for the skyrocketing steel prices.
I wouldn't even be considering this whole thing but if things go according to plan, which they never do, my light at the end of the tunnel is having two trucks and trailers paid for in 5 years.. Then I'll likely cash out and do something different.

 

[PackRat]

Are you sure you can get a Detroit in a Pete? I was under the impression that they are only available in Daimler trucks.

I hate the idea of a Paccar truck with anything but a Cat or Cummins in it, but if it saves fuel I think I could stomach it, as long as the fuel savings work out to be more than the hit the truck would take for resale value.

I was informed, by the salesman that has dealt with our company for years, that PACCAR has denied all requests for Detroits, since they were acquired by DC. I imagine, however, if a fleet customer wanted to order a large number of Pete's with Detroits, or would go the Freightshaker to get the Detroit, I'd bet PACCAR would fold pretty quickly.

Cam, why are you going with the 70"? Seems like a 63" would suffice, and save you quite a bit in manuverability, weight, and fuel.

All things considered, I'd sit down with a knowlegeable Pete rep, and see what you could shake out.

Also, I'm not sure the Autoshift would make a big differnce in mileage, but would probably pay out better, on the resale end. They do say that it is easier on the powertrain, which might save you some $$ on maintenance, in the long run. We have very mixed reviews on the Auto, from drivers. Some think its the best idea ever, others hate it with a passion.

 

[Camstyn]

I want to go with the 70" to keep the drivers happy more than anything, one of them being me. It actually seems kinda small compared to Western Star's 82" stratosphere, or Kenworth's 86" studio