well on a new thread i have a 2000 Durango R/T 5.9L i know 5.9L engine is not going to get much mpg but with warming it up for about 5-8 mins b4 driving and driving honestly pretty weak no hard or fast accel speed limits here around all around 25mph im easy on the gas for the most part most ppl when leaving a start light pile up behind me lol i do bc its 157k miles and its my only vehicle i have to try make it last at lest a year.. had problems with ignition coil rescently had to replace it. but even so im only getting about 8MPG on highway 8.9 the durango has a computer thing that tells me my MPG. also iv checked it using a full tank *premium fuel* it is required on the R/T. but with using the milage i get from a full tank to empty. i have ran sea foam thru the fuel system and oil its got fresh 5-30 full synthetic oil. good plugs irodium Ix from NGK and new cap wires 7mm. and new ignition coil now. and still im maxing at 8.9MPH highway and 8MPG city that cant be normal? is it. was thinking maybe it could be the tiny dinky battery in it or more possible the TPS. it has a hard time shifting somtimes esp downshift and its just got a tranny rebuild 3 months ago. but going up hill it will slowly like low power getting up go up to 3.5k rpm then shift and sound really really boged down then shift up again and putt up the hill then shift down and haev 3.5k rpm then up again and it repeats over n over till i top the hill. then on the way down it just draggs n backfires like a high end drag car at the end of a race or a 18wheeler coming to a stop. its got flowmasters on it so its pretty loud. also if im in park if i rev it up it sounds like its running up nice n fine but then fights it self as it lowers RPM and backfires like not big bag backfire on a old car but quick little pops like i said a high end dragcar slowing down.. kinda like the sound really. but not shure if it SHOULD sound /act like that. and the MPG is killer... esp on premium gas.

 

Those plugs might be part of the problem. You need to get some plain old champion copper core plugs gapped to .040". The sounds you're hearing on the overrun should be normal.

 

so going from 7$ new tec spark plugs to just 2$ copper plugs might help my MPG?
http://www.autozone.com/autozone/par..._657731_18342_ thats all i found that fit my durango, walmart/advance dont have anything from champion that fit it. i thought about E3's any comment on them?

 

Yeah these engines don't like those fancy plugs, they just like the normal copper core ones, which makes sense when you think about it; the ignition system was designed around the copper core plugs. Those goofy new plugs can cause all kinds of running issues. I'm sure that all the parts stores have them (walmart is useless), just ask for regular copper core champions for a Dodge 5.9.

 

I always hated Champion plugs, have seen too many new champions cause more misfires than any other brands from cracking. I always used NGK, Nippondenso, Bosch, or AC Delco(GM days). Using platinums will sometimes screw with the ignition but never had that happen yet on any of my 70+ vehicles. Hopefully Champion has improved their quality over the last 15 years.