Fuel economy

Kevin_Sue · Apr 17, 2007

Hi

What can be the expected overall fuel economy for a "d" unit. The truck will have an automatic transmission. Most likley a freightliner m2 but also considering peterbilt, Kenworth, International and Hino. I am looking for a good low mile truck and am trying to find the best overall value and fuel economy will play a large part in the overall life cycle of the truck.

LDB · Apr 17, 2007

I set my spreadsheet up using 7.5 mpg even though I get 8 at least. I set up all my cost categories higher than they are. If a run still makes money then I know it's ok since it is going to make more than the spreadsheet suggests. You'll hear reports as high as 11-12mpg for a D unit. Do your calculations on something like 7-8. If you show a profit that way then if/when you get better mpg your profit will go up. Good luck.

Leo Bricker, 73's K5LDB, OOIDA Life Member 677319
Owner, Panther trucks 5508, 5509, 5641
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gbuck302000 · Apr 17, 2007

i wouldn't consider a m2 if you want good fuel economy.the one in our fleet with the cat c-9 and allison 6sp auto only averages 7 mpg loaded light and running 70mph not very impressive!!!

arkjarhead · Apr 17, 2007

i drove an M2 with a cummins motor and a 10 speed manual and it got averaged 9.5 mpg. alot has to do with the powertrain setup.

highway star · Apr 17, 2007

'07 M2, 250 MBE, 6 speed MBE auto-shift. The Freightliner computer says it was getting 10mpg with 6500 miles on the clock. At around 4k I checked it and got 8.75. That was with some generator use and going back and forth on I-80 through Pa.

x06col · Apr 17, 2007

Gobuck, are you still going 70 on this thread?? Thats plenty!!!

JohnO · Apr 17, 2007

Iâ€™m driving a 1998 FL70, 651,000 miles, dual 75 gallon tanks, 3126 CAT, Allision 6 speed automatic, 84â€ bentz sleeper, 22â€™ dry box, 2,500 lb liftgate, steer 10,500lbs, drive 13,100lbs.

55 mpg mostly non hilly highway miles I average 11.09 mpg to 10.298mpg

60 mpg mostly non hilly highway miles I average 10.15mpg to 9.50mpg

55mpg hilly highway like I-64 through VA and WV I average 10.15mpg

60 mpg hilly highway like I-64 through VA and WV I average 9.5mpg to 9.15mpg

Average load onboard 2500lbs
Though once hauled 13,500lbs what a difference climbing hills with that onboard.

Come on Nelly Belle you can make.

A side note who or what was â€œNelly Belleâ€?

ATeam · Apr 17, 2007

As you see, it is a much simpler question to ask than it is to answer. That is because so many variables apply (truck weight, engine, transmission, rear axle ratio, axle configuration, aerodynamic shape, etc.).

In the Class 8 fleet owner trucks we drove, fuel economy ranged from 6.5 to 9.5 mpg average, depending on truck configuration. The best truck had a Detroit 500 engine, Eaton 10 speed auto-shift transmission and a good rear axle ratio (sorry, don't remember exactly what it was). The worst truck was also a Freightliner Century Class truck with the same engine but a 6 speed automatic transmission. The difference between the two was a full 3 mpg, which can add up real fast in dollar terms.

In general terms, our current truck gets 9 mpg at 65 mpg and 10 mpg at 55 mpg. Those numbers vary with wind and terrain. Note that our truck is heavier than most C-units out there at 34,000 lbs. (weight of truck with full tanks, no freight).

Also note that trucks that are for sale tend to have better fuel economy numbers attributed to them than those that are not.

gbuck302000 · Apr 17, 2007

>Gobuck, are you still going 70 on this thread?? Thats
>plenty!!!
haha funny maybe it will do better with a "slower" driver behind the wheel...in all reality i would steer clear of the c-9 i heard rumor that cat is no longer going to produce this engine because of poor fuel efficency and many other problems..

simon says · Apr 20, 2007

Yes: C-9 is history. I doubt it had much to do with fuel efficiency however. The problem was those engines were mated to Allisons, and mostly 5 spds? Need to be careful when spec'g 6 speed Allisons, so top gear is not such a low ratio. Secondly, and primary, is that the engine was redundant: not popular enough to warrant manufacture and probably couldn't meet 07 specs. ISL is still available- if you can find a truck to put it in.
My ISC-315 is mated to a .74 final, 4.10 RA, can max 88 mph, and gets about 8.5-9.5. I can climb hills very well. There is a reason that engine manufacturers offer programs to compute what is the best set-up. Mine runs at 1538 at 60 mph. If I stay between 60-65, I can do well, pending wind, terrain, some idling, etc.