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-   -   11 mpg! (http://www.ramforumz.com/showthread.php?t=150891)

OXlvsMPR85 08-20-2013 07:30 AM

11 mpg!
 
Just bought my 99, 1500, 5.9 and I already replaced the crank seal and rear main seal, the truck runs great but the mileage is horrible. I plan on doing a tune up but when I search for a tune kit (ie: plugs, wires, cap and rotor) there are so many options for how hot the plugs burn or what not.... I'm trying not to go with OEM on this and I'm not looking for a entire ignition system, but if anyone might know how hot of a plug and coil a 5.9 can run that would be great or even just a good tune kit. Thanks for your time everyone.

panhead 08-20-2013 06:39 PM

Stay away from Champion spark plugs. Full tune up (cap/dis rotor, wires, Autolite spark plugs). Get an ignition coil, either from Mopar or Accel. Replacing O2 sensors will improve MPG's.

the persuader 08-20-2013 10:47 PM

Is that 11 mpg in town? If so, that might be the best you're gonna get. These trucks aren't great in the gas mileage department. My truck gets 10-11 city, 13-14 hwy

If it is highway, you have issues. I once got 9.5 mpg on the highway when my plenum gasket was bad.

richmond 08-21-2013 12:04 AM

Ditto that of Panhead & Persuader
 
I did Autolite plugs and Mopar ignition coil the last time (2 years ago). I've been running town trips in my 98 Larime 5.9 4X4 Quad grabbing parts for a truck I picked up. My 5 trips into town and back, the best I could muster was 10 mpg. I cracked 15mpg once going to Louisville and back. Like Persuader I'm happy with my truck, crappy mileage and all. I think we're probably stuck in this range (as long as we keep'em in tuned up).

R...

OXlvsMPR85 08-21-2013 08:11 AM

Well that all makes sense... we all did not buy these trucks for the mileage, but i drive it mostly on the highway. I do however need my timing cover, and plenum gaskets replaced. While that's all apart I'm going to replace the thermostat and O2 sensor and see how we do after that.

the persuader 08-21-2013 11:02 AM

My Hughes plenum kit came with a thermostat, but it looks like they don't include them anymore. I will say that I was impressed with the kit. Came with everything I needed except for blue threadlocker and RTV.

http://www.hughesengines.com/Index/p...p?partid=27091

If your 02 sensors are bad, that can cause a gas mileage drop.

tjbiker031 08-21-2013 12:13 PM

Quote:

Originally Posted by OXlvsMPR85 (Post 1181598)
Well that all makes sense... we all did not buy these trucks for the mileage, but i drive it mostly on the highway. I do however need my timing cover, and plenum gaskets replaced. While that's all apart I'm going to replace the thermostat and O2 sensor and see how we do after that.

I will tell you that with new O2 sensors you MAY see slightly better IF they are bad. Honstly those dont go bad that often unless you are running the engine rich

As far as the thermostat goes. Buy an OEM one. If you get one that runs the engine colder (or warmer) than the OEM spec are...you WILL get horrible gas milage. Running a "cooler" Thermostat will hinder performance by not allowing it to reach proper operational temp to properly burn A/F mixture...along other emission issues it will cause also tearing up MPG efficiancy. The old-timers sayin that running a cooler or colder thermostat will help your engine last is a myth and will eventually destroy your engine.

05SilverStreak 08-21-2013 10:09 PM

Sounds great! My 98 gets a whopping 14mpg going downhill with the engine off and wind behind it.

Gantman 08-21-2013 10:23 PM

Man you get slightly better average than my old 99 5.9 Magnum. I barely averaged 10 city/hwy mix when I had her. But I drove it like I stole it back in those days.

tmaxxs10 08-23-2013 11:57 AM

Go wit the Hughes plate kit or the air gap intake. I would also do a timing chain while you have the cover off. You may as well do a water pump since it's off. As for plugs I think I am going to try ngk plugs or molar performance. From experience replace as much as you can if you have it apart.


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