12 Valve 2nd Gen Dodge Cummins 94-98 Discussion of 12 Valve 5.9 Liter Dodge Cummins Diesels with P7100 Injection Pumps

Bad MPG in my 12 valve

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Old May 12, 2016 | 08:02 PM
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Default Bad MPG in my 12 valve

I'm new here so help me out if i do something wrong. my question for you guys is how can i get better mileage in my 97. i currently get around 9 in town, i am going fast sometimes so i don't baby it around all the time but for the most part i do. i don't do much highway driving but last summer when i drove to the beach i got about 20-21 on the highway.

my truck is a 97 12 valve hx35, 5'' straight pipe, K&N cold air intake, 4k gov, tuned pump, full cut delivery valves, pusher intake horn. 2.5" leveling kit on 20x12 fuels with 33" mud graps.

i need help! i need better MPGs, any suggestions????
 
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Old May 13, 2016 | 04:10 PM
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Tighter TC.
 
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Old May 13, 2016 | 08:00 PM
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full cuts, get rid of them. get normal dv back in there and see how it runs. the street is no place for full cuts. afc live after could help refine your tuning. timing it can give you better mpg but you will need studs, and i sure hope you have valve springs for that 4 gsk
 
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Old May 14, 2016 | 05:58 AM
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He's getting over 20 on the highway, that's about as efficient as that pump can get with those tires.
 
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Old May 15, 2016 | 01:25 PM
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Last year he was. Could have had stock dv's last year
 
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Old May 15, 2016 | 04:35 PM
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True. Still, DV's don't do anything your foot doesn't tell them to. Lots of info on the engine combo, nothing here on the trans. I picked up 4mpg around town with a tighter TC, and drove it harder.
 
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Old May 19, 2016 | 04:59 PM
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thanks for the replies guys! yes last year the truck was all stock except for exhaust and intake also i didn't have the mud tires on i just had A/T's. also i of have the valve springs done too.

so this week i have been really babying it keeping the RPMs under 2k. i have seen a very good increase in economy i should be around 14 now in town, its just no fun i guess this is just what its gonna have to be.

once again thanks for the replies!!
 
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Old May 19, 2016 | 05:17 PM
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That's still no good, I don't have to baby it much to average at least 16s around town. What's been done to you trans?
 
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Old May 19, 2016 | 06:27 PM
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Nothing at all. At least not that I know of. It's starting to slip a little so I know it's about time to upgrade
 
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Old May 20, 2016 | 05:21 PM
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Considering slip is mostly what the stock trans does anyway, then yeah. Get a good low stall super single TC, and don't be surprised when your mileage goes up. Unless you plan to do big turbo work, in which case low stall would be a problem, but.
 
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