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I'm wondering if anyone knows which engine would be best for MPG in a hobby truck that will be lightly loaded 99% of the time (maybe hauling a couple of antique pickups on a drop deck trailer or a fifth wheel RV or similar).  Not looking to haul 80,000 lbs on a regular basis, if ever.  Logically, I would think an E6 would return the best fuel economy pulling light loads but you often hear people say that large-displacement, lightly-stressed engines actually outperform the small-displacement engines for economy-- although I'm assuming that's pulling full-gross loads. 

Does anyone have any experience with these motors pulling lighter loads like a hobby truck typically would?  I've always thought an E6 would make a lot of sense in a hobby truck but I want to make sure I'm not missing something.  Thanks for your input!  

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In my experience e6 will always come up better. Both my e9's stay pretty consistent at 4.2 to 4.5 mpg regardless of load. 

If it's just a hobby truck then skip the fuel mileage and just go e9!! 

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Not considering injector flow rates. You can kind of look at it this way. Each revolution an E-9 will have four injector strokes. An E-6/E-7 three injector strokes. A 671 6 injector strokes and so on.

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I never measured my fuel consumption on my E9 MH, I doubt if it was better than a six, my only concern was getting the cooling system to come up to temp when bobtailing, that alone will make fuel burn inefficient to a point where I was going to blank off most of the rad to see if it helped.... loaded trailer, no problem.

For sheer "grin factor" on a hobby truck, go E9, but just consider how much it will cost to repair if it goes bang, then you wish you had a E6... LOL

BC Mack

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36 minutes ago, sodly said:

Sorry... what is "bugger all"?  Ignorant American speaking here.   

Sorry, bugger all means very little. 

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I would have to ask Ray what he gets bob tailing or dragging his empty flat bed.  I do know a 300 mack with a mack 9 speed overdrive got me in the high 6's with a empty van trailer from Long island to Chicago. never did get good MPG with a 300 and direct 6 speed best I think was 5.8

 

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my e-9 loaded one way (98,000) and hauling empty apple bins as a back haul (46,000)13.6 high  avg. 15 gal/ hr.

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Anyone have MPGs of E9s bobtailing or pulling empty trailers?  How about E6s?  Kinda makes me wonder if Timmyb is right.  Perhaps lightly loaded (or empty) there wouldn't be much difference at all.

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My E 6 300 with 9 speed O/D and 4.0 rear will get right above 10.0 bobtail. 

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17 hours ago, MHfred said:

My E 6 300 with 9 speed O/D and 4.0 rear will get right above 10.0 bobtail. 

That's about what I had with my E6-350 R-model bobtailing for nearly 1500 km. T2090 0.71 OD tranny with 5.02 rears on 11R24.5.

Here we use a different style of counting consumption. How many liters you burn passing each 100 km. So I had to do some math.

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My superliner with e6 350 "pump has been played with not by me previous owner had to of" t2100 10sp with 3.86 "I think" 11R22.5 I average 6.5 running 65-70 or almost 7 if I never go over 60 during the day. That's 80000ish one way empty coming back pulling a low sided hopper 

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