12 valve fuel mileage - Diesel Bombers



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

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Old 10-08-2010, 11:13 PM
bean farms's Avatar
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Default 12 valve fuel mileage

i have a 98 12valve with twins,4"ex,4kgs,timming at 14.5*,100 fuel plate half forward star wheel turned almost all the way on smoke screw just touching. my fuel mileage has drop from 18.5 to 15 under normal driving conditions what could cause this new air filter and fuel filter on it. it has the original injectors and 275,000 miles on it i ordered some new ones i needed them for my twins any way i got 5x.014 sdx for it do yall think my injectors could cause the drop in fuel economy thanks

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any ideas

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any clue

Last edited by bean farms; 10-08-2010 at 11:13 PM. Reason: Automerged Doublepost
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Old 10-08-2010, 11:18 PM
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Over how many tanks of fuel? Also Bump the timing to 16.5, mine loves it there. New injectors should help, the old ones can be causeing some issues. Anything else different goin on with the truck? Do you guys get winter blend fuel down there? Places up here are switching to it again to it up here and my rigs always get worse milage with it.
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Old 10-09-2010, 01:54 AM
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i'd say your stock injectors probably have something to do with it with the twin set up and also last time you changed all your fluids and filters?
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Old 10-11-2010, 01:06 AM
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everything has been serviced reacently and its been goin on for a little while now even befor i got my twins no winter fuel around here yet i cant figure it out nothing has rely changed on the truck but the mileage
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Old 10-15-2010, 05:01 PM
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Loss of mileage is one of the textbook normal signs of slipped timing. When they slip it always retards it. Likewise, loss of power (particularly at high rpm) is completely normal also when it slips.
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