I am trying a number of methods, both conventional and unconventional, to boost the gas mileage in my 1999 Durango, 5.9L 225,000 km on it.

I have for a year or so been running with a K&N air filter, Mobil 1 oil, Autolite 3923 plugs, synthetic gear oil in the rear end. I've never had any problems with this vehicle, and we have made trips from northern Alberta to San Diego, and Nevada, both times pulling a holiday trailer.

Baseline test - each of my tests involve the same mainly highway circuit of 70km/50 miles. I am trying to purchase fuel from the same station, same pump. Initial mileage = 20.14 mpg. This is probably the highest I have ever seen it, considering I need an oil change and the air filter needs cleaning. On reflection I probably should have done a longer baseline test.

Installed Haloplugs - according to the instructions as shipped with these plugs, the battery must be disconnected to allow the computer to reset itself so it works properly with these new plugs? Sounds kind of fishy, however I follow the instructions. Mileage now shows = 16.45 mpg. Not off to a good start [>:]

Overdue for a transmission fluid and filter change. I've never done it myself before, and probably will never again. Making a mess is almost unavoidable. Changed PCV valve as it is overdue. After finishing, I take another test run = 18.8 mpg. Still not great.

Considering these plugs might require a "stronger spark" than normal plugs, and I have never changed the plug wires or distributor cap and rotor, I decide to install a set of Bosch wires, cap and rotor. Also cleaned the K&N filter. Result of this test run = 25.25 mpg
INACCURATE! SEE BELOW!

I will continue to do some test runs over the next few weeks, and I'll post my results here. I will probably reinstall a set of Autolite plugs and see what happens to my gas mileage.

Have any of you other Durango owners tried these plugs? What kind of results did you see? The company advertises "increases fuel economy up to 10%" which sounds a "bit" optimistic.[/align]

 

Is your D a 4x4 or 4x2?

I only average 12/14 . 16 was my best. would love to see anything higher consistently but doubt this will happen.

I always do a severe maintenance schedule. Meaning, 5k syn oil changes, yearly replacement of all fluids (tranny, axle, etc.).

Bosch wires and their plantinum plugs don't do well for the 5.2/5.9 family engines.

I must assume where you drive and get this high mpg's must be flat plains most of the time.

 

if you got 20 mpg before and are getting 25 now, thats 25% increase (minus the filter cleaning and whanot)...id say thats outstanding! (assuming the tests hold water when you put the old plugs back in.)
good luck on that and deff keep us posted!

 

amazing mileage!! I hope i can pull off something like that.. put up a part number if you can for these plugs...

as a sidenote, its good to see somebody else here using the metric system

 

I'm sorry, but I don't buy that you're getting over 25 mpg with the 5.9L V8

 

Hey, I don't buy it either. That is why I am going to continue doing mileage tests. My "loop" is 50 miles, mostly highway, one very large hill and a couple of smaller ones. Other than that, it is flat highway. Personally I can't believe a set of plugs could make that much difference. I was expecting the same or worse mileage than the Autolite plugs I had in there.

I am an old bugger (relatively speaking, as I am under 50)and still have to convert back to standard for things to make sense.

You can search on the net for Haloplugs. I am not going to post either a link or a part number unless these things prove out.

4x4

I never see more than about 12.8 mpg city driving, unless I use a real light foot. Hauling my holiday trailer I was seeing between 10 and 11 mpg. 8 or less on hills.

I don't see how the wires "don't do well". Plugs maybe. Someone said those Autolites were the best to use, after a year they had almost zero carbon on them.

 

Something is wrong with these numbers. If you were seeing 12 mpg, there's no way you jumped to over 25 mpg with ANY plug and/or wire change.

You need bigger samples than just 50 miles. Plus, how are you figuring your mpg?

 

UPDATE - ABOVE MILEAGE NOT ACCURATE:
After a test run today, it took far more to top up the tank than it should have. So I must not have completely topped the tank up after that test, which showed less fuel used than actual.

I might have a 600 mile trip coming up - if so, then I am going to run the Haloplugs one way, and a new set of Autolite plugs on the way back and compare.

"If you were seeing 12 mpg, there's no way you jumped to over 25 mpg" - I didn't sayI was getting 12 mpg, read my post again. Slightly over 12 in the city, and between 16.5 and 20 on the highway, although I don't trust the gas mileage on my first test.

I use my trip meter and the amount of fuel used to top up my tank to calculate my mileage. Not exactly lab conditions, but the best I can do. Truck has factory size tires, btw.

 

So what was your mpg on this test run?

 

I still kinda doubt spark plugs alone can give you that much increase in fuel savings. If anyone remembers, I posted a message in this forum concerning the Pulse spark plugs at around $25 a pop and they say it can give you up to 25 percent increase in mpg and power. but at $25 a pop multiplied by 8 is hard make the decision to buy and try.

here is the message thread I posted about the Pulstar plug. Compare this to the Haloplug and let us know what you think?

https://dodgeforum.com/m_885896/tm.htm