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I posted a question here in the general section, but how is it that I have a 6-71 238n and get 4-5 mpg pulling 60-65k local ang the big guys only get 5-6 maby with 3406b cats or dd16 in a a newer tractor doing the same work ? local running demo trailers 35-40 mile speed limits it does ok with the three car trailer as total weight is 30k or so and gets 7-8 on a good day you think that less hp should give more mileage local ? ps still makes the same money as a new tractor .........
 

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I posted a question here in the general section, but how is it that I have a 6-71 238n and get 4-5 mpg pulling 60-65k local ang the big guys only get 5-6 maby with 3406b cats or dd16 in a a newer tractor doing the same work ? local running demo trailers 35-40 mile speed limits it does ok with the three car trailer as total weight is 30k or so and gets 7-8 on a good day you think that less hp should give more mileage local ? ps still makes the same money as a new tractor .........
The reason is you're running an N engine for one and for two it's a two stroke. Detroit came out with their last gasp at making the engine competitive with Cummins and Cat by making the Silver Series. This changed the pistons, liners, rods, injectors, blowers etc to try and improve fuel mileage and emissions down. It came close, but still wasn't going to meet the newer EPA rules coming out in the future. This is when they decided to design the 60 series. If you wanted to get better fuel mileage you'd have to upgrade to Silver spec or at least upgrade to turbo and after cooler.
 
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