A lot of times the same code will keep recurring.

 

i for one am not a fan of the volvo motors. i used to run a day cab with the vd12 or whatever they call it in a 04 volvo. the worst motor i ever drove. foot always in it. then again i think there was issues with it. on flat ground it would just slow down for no reason.

anyway, i'm a die hard cummins fan. when i was looking for trucks a few months back i wanted a isx. i called up and talked to some people. they said that they'll get well in to the 7's. (old fleet trucks). maybe this is true.. but what is the speed limited to? my company truck now is a day cab columbia with a s60. its limited to 65, i 90& of the time get anywhere from 7-7.5. before it was turned down it would run about 74. i would get anywhere between 6.75-7.1. we do run light though. anyway. my truck went down a few weeks back and i got a columbia with a c15.. it got just over 5. but there has to be a way to pull mpg out of them.. i'm noticing a lot of fleets are running c15's now. guess its all in how you drive and the load.

 

It is so hard to compare engines because there are so many ways to set up a truck and so many applications a truck can be used in. Also, studies have been shown that there is at least a 20% difference in fuel economy between the best and worse drivers under identical situations. Cummins covers the topic of fuel economy quite well in the PDF document at the following address:

http://www.everytime.cummins.com/ass...Whitepaper.pdf

While I’ve never owned one, Detroit has always had a good reputation when it comes to fuel economy (one of the primary reasons a lot of big companies run them) and they are easy to find service for out on the road. My 2003 CAT C-15 had a lifetime average (in the 645k miles that I put on it) of 6.2 mpg. My 2006 ISX was averaging 6.7 mpg before I unplugged my EGR, and since has gone up to 7.2 mpg in mostly winter driving, which always hurts economy.

Finally, keep in mind when talking to people about their own fuel economy that there are several ways to derive their economy numbers. Some will simply look at their ECM report or go by what their computerized in-dash display tells them. Both of these methods will yield inaccurate data. The only way to accurately figure and track fuel economy is by the “at the pump” numbers. Take the miles you have driven since your last fill-up and divide by the gallons required to fill your tank(s) back up. I do this with every fuel purchase from the first day I buy a truck and keep the data forever in an Excel spreadsheet so I can analyze trends that might take many tens of thousands of miles to develop.

 

was thinking about upgrading my old Volvo (1999) with Cummins N14 for a Freightliner with Cummins ISX on which EGR will be turned off immedeately (Thanks to your posts of cause! ) . Right now I got 6.7-7.0 depending on speed. Usually when I'm doing my IFTA it around 6.8

 

When I was driving my 2001 Mack with 460 hp Mack E-7 engine, it would take considerable effort on my part to get below 6.6 mpg. Many times I was up around 7. Then I was in a 2009 Pete with 550 hp Cummins ISX and it stayed at 4.5 mpg no matter what.

My bullhauling partner drove an old Freighliner FLD with a 525 hp Detroit and he usually got around 6 mpg.

You asked for advice: I say stay away from new engines if you're looking for fuel economy.

 

and you can't hardly trace down the problems when you have wiring problems.

 

1998 T800 11L M11 Cummins 370/410 13 spd OD 4.33 rear = 6.0 mpUSg winter at 60 - 65 mph in NY state

2008 T660 14L ISX Cummins 485/485 13 spd OD 3.9 rear = 5.0 mpUSg winter at 60 - 65 mph in NY state

 

the more I read about newer trucks the more I want to keep my ole one. at 60-65 mp.h I'll ave 6.25-6.75 m.p.g. not to mention the parts for my 11.1 ser 60 det are dirt cheap compared to newer ones. I talked to 1 of our drivers yesterday, have not seen him in a week. said he was having injectors put in. $ 4000,00 from thompson cat. I told him I had my put in by a local dealer last year. dropped truck off at 3 p.m. & picked up truck at 10:30 pm that same night. 2,400 for everything. including a new e.c.m wiring harness.

he said yeah but I got the yellow motor. he get's 5 m.p.g. if lucky. I got a price on a turbo for my truck. $650.00 not bad considering what I hear the rates for newer trucks. I am not knocking cat or what anyone has. the new det's are a lot more money for their parts than mine are too. turbo still original 1.3 mi miles.

 

I hate new trucks.

This '08 T660 is the same darn truck as our '95 T600 and '98 T800. Matter if fact lots of stuff isn't as good.....like whose idea was it to switch from toggle switches to rockers? And those aero dynamic mirrors still vibrate like they did 13 years ago. And you still have to make a choice between warm feet and a clear windshield because you can't have both. And don't get me started on DPF's and EGR and bad/unproven designs like EGR coolers going bad and a new starter every year and a new turbo in the first year.

But they are more quiet.

 

I like noise & a rough ride.. it keeps me awake. lol. $15,000 over 11 years ago for my truck & I am still driving it. that is why I like what I have.