Get rid of that supershit chips stuff. First off the 5.9 out of the factory is a gas hungry mother f... And trying to pump more fuel in to the chamber for more HP then you're going to suffer in MPG. If you want to keep your super MPG sucker then you will need to drop the axle ratio but you won't be able to pull much weight if you go to low. These dodge trucks are only good to mod into performance if you are rich.

 

Well that's my problem, I own a lawn care service and pull a trailer all the time... and The superchips is always on either tow mode or gas saver mode, depending on weather im pulling a trailer or not. But either way, I should be getting better than 7 MPG...

 

Revert the fuel system back to stock, keep the 3.55 Ratio and double dose on some Valvoline Fuel Injector-Intake Valve Cleaner. Also clean the throttle body and IAC valve, you want to have as much air as you can mixed with the fuel cause then it won't have to run rich or lean just right. The super chip things I stay away from those because they don't always do good, obviously you are saying you're getting only 7 MPG, and well I'm not going to lie but that is pitiful. Now I had the 5.9L but in a conversion van and that thing was horrible on gas I mean you put the key in the ignition and the needle would fall out. So try doing what I said and if that does no good then it ends up being limited to what can be done, thing is you don't want to force it to run lean because it will fail trying to tow and you don't want it running rich period.

 

id have to agree with the superchip. i think a custom tune would do better than the superchip, im not sure where or how to get em but from what ive read on here over time someone else would know.
i cant beleive that 7mpg lol.
my buddys v10 he had not too long ago got about 9 to 10
and i have a different buddy who has the same exact truck as you and is getting 16.5 mpg. YEA i didnt beleive him at first lol. without any mods of course lol.

 

Get rid of that supershit chips stuff.

Superchips will not hurt, it is an actual tuner, not just a "chip". It will not dump fuel and make it run rich or anything like that, it will actually help the engine to produce more power and be more efficient. I've never seen anyone with a superchips or diablo sport that got worse gas mileage or anything or that nature...I picked up mpg with my superchips, and all my friends that have used superchips and diablo on their various vehicles all got better mpg. Now with the tow tune I'd expect your mpg to remain the same...Also keep in mind if your pulling a trailer that decreases your mpg, also 4wd decreases your mpg even when not engaged.

Do you have any check engine lights on or anything like that? My first thought when I saw you replaced your cats and the rest of the exhaust was O2 sensors. Did you run the engine at all with with the exhaust off before installing the new exhaust? If you start the engine with the O2 sensors near the end of the exhaust pipe it will ruin the sensors. Also, do you have O2 simulators or anything else similar to this? This could mess with your gas mileage...

 

Two other things I'd try are: Maybe try running an oem type spark plug, I've seen instances when just plugs alone will cause poor performance and mpg. also I am not positive but I don't think spectre CAI are actually cold air intakes...if the filter is open to the hot air under the hood this would hurt performance over the stock intake. Need to grab cooler air from outside of the engine bay.

 

No CEL or anything of that nature. I replaced the O2 sensors along with the rest of the exhaust and never started it untill it was done. No simulators or anything. The only stuff I have is what I listed. And as far as the Superchips goes, I get worse without it!!!! I used to have another 99 about 5 years ago that did get 13-14, That's why this has me so baffled!!! :doh:

 

When you did all these tests and compared them with other vehicles, was the test vehicle towing anything? And what kind of cargo was their?

I am someone interested in why it's killing on MPG as well, I'm thinking somewhere along the lines as a fuel injection issue maybe, or their is some kind of load that is killing. I can tell you that usually larger tires kill alot of things but sometimes they do help. Their is a chart that will give you a result of efficency based on axle ratio, engine size, tire size, and weight, among other variables. I just can't remember where this chart was, I was looking up chrysler TSB's so I will look there if I find it I will give it to you. Anyway's I try to stay away from performance mods, the only mod's I will ever do in terms of performance and duty would have to be done to the transmission. That's the only thing I would mod. But I can tell you that the 5.9L is death on the fuel. I have had a 5.9 and got rid of it because mainly the gas. I drive a 5.2 and it's much better and some people with their 3.9 are happy as pigs in... Because I know they get decent MPG, though not the best in the world. Well anyways if I find the chart I will send it to you.

 

At the very least I'd pull the intake and replace the plenum gasket. Normally when they fail, the truck runs worse and worse. In your case, with the aftermarket stuff may be minimizing some of the usual symptoms, but you can't hide from poor mileage. I have a '93 360 mag 3/4 ton with 4.11 rear and taller than stock rear tires that probably put the final drive into the mid-3's. Haulin' it down I-10 75-80mph and it knocks down a smidgen over 15mpg. Have you reset the computer?

 

I don't think I have reset the computer... how do I do that? and i have already replaced that gasket, forgot to mention that earlier.

 

Keep in mind after reset your system will need to run a couple hundred mikes to re-learn the basics, but a reset is sometimes a necessary deal. A computer is reset with the code reader tools, but a shade tree reset can be done by simply pulling the battery cable off for a few minutes (my method of choice). One may also pull both battery cables off, touch together, then re-attach to battery. Either way, the computer will reset to baseline.

 

MPG Gains

I saw your thread & I have a 98 Ram 1500 5.9 & I have done tons to it & get 20MPG+ per tank. Here is what you do.

E3 Sparkplugs
MSD Coil & Wires
Air Intake with K&N Filter
Synthetic 5w20 Oil & K&N Filter
Synthetic Tranny Fluid
Synthetic Differential Fluid Change(every 50K)
Remove Motor Fan - Install Electric Fans
Superchips Flashpaq Prog - Set on Mileage XS
Use Hypermiling Techniques - Coast when possible
TBI 1" Spacer
Headers & Dual Exhaust CherryBomb Glasspaqs
New GBH Bearings packed in Synthetic Grease


The two best things from the list is (1) Hypermiling Techniques & the SC Flashpaq Programmer set on Mileage XS

I ABSOLUTELY HATE paying for fuel, here in the Toronto area gas is about $4.40 USD per gallon which hurts like hell when filling up!

 

I saw your thread & I have a 98 Ram 1500 5.9 & I have done tons to it & get 20MPG+ per tank. Here is what you do.

E3 Sparkplugs
MSD Coil & Wires
Air Intake with K&N Filter
Synthetic 5w20 Oil & K&N Filter
Synthetic Tranny Fluid
Synthetic Differential Fluid Change(every 50K)
Remove Motor Fan - Install Electric Fans
Superchips Flashpaq Prog - Set on Mileage XS
Use Hypermiling Techniques - Coast when possible
TBI 1" Spacer
Headers & Dual Exhaust CherryBomb Glasspaqs
New GBH Bearings packed in Synthetic Grease


The two best things from the list is (1) Hypermiling Techniques & the SC Flashpaq Programmer set on Mileage XS

I ABSOLUTELY HATE paying for fuel, here in the Toronto area gas is about $4.40 USD per gallon which hurts like hell when filling up!

Are you for real? 20mpg? Are you all highway? I'm assuming the electric fan had to make a big difference. Hypermiling? I'm guessing that is the major difference. That's a lot of work when you're driving in order to save some money, but I guess everyone has their own priorities.

 

Mpg

I forgot to put in I put on a new tensioner pulley & belt, also tire PSI is at 55PSI.

 

is DRAM1500 the same person who posted another thread about achieving like 24mpg or something in city and 30mpg + on hwy.....?

 

Well I have an update My mileage has gone from 7.3 to 8.8, and the only thing that have changed is the gas I'm using. Since we moved recently I have quit using QT gas and started using BP, because it is right up the street. I have been reading that their gas is a whole lot better than QT. So that's a heads up for others to try. The other thing is we have gone from low 100 degree temps to mid to low 80's now. The next strep I'm going to take is changing the diff fluids and transfer case fluid. I want to do the trans but I don't want to mess up a working tranny with the way these dodges are lol. So... What fluids do you all suggest I use in the diff's and trans case????

 

Well I can only speak for the older transmissions and what I have to say is that they are great transmissions believe it or not, the reason why people have begun to say they suck and a reputation has built up is because of things you are not doing. It's when you don't maintain the transmission does it start acting up also the biggest thing is when you take it to a mechanic and they decide to use Dex or Merc instead of ATF+3/4. So my recommendation to you is to bring it to a good transmission shop and have them flush it and adjust the bands and replace the filter. Make sure they use a rubber gasket instead of cork and never use RTV as it isn't impregnable to ATF. As for fluid recommendations I have always made well with Valvoline I use Valvoline as my transmission fluid, engine oil, gear oil, brake fluid, power steer fluid, fuel inject cleaner, and more... As for filters I just use the standard chrysler oem oil filter as I tried fram and it had a leak and tried wix and all them and they did fine but I figure let me just use the oem it's only a couple dollars more then a fram. As for the transmission filter I buy the transmission filter kit from advanced auto made by Pro King, come with two gaskets for the two different pans. Then for the air filter I just use a fram. But as far as fluids I trust Valvoline my family has and I get excellent results. This is just from my use and my opinion. The only fluid that I use that isn't valvoline right now is the anti freeze because my local autoparts stores don't sell valvoline's antifreeze so I would have to order it online and I figure I change the fluid out every year or so and use distilled water so it should be fine. I do recommend if you need to clean your radiator you can just use that peak flush and cleaner stuff I need two bottles cause of the size of my system but you as well could, I run it with distilled water for a little over a week on off driving, I do that because I'm prone to clogs and had one on the highway and you can guess I did overheat a little but I slowed down and drafted behind a tractor trailer with the heat on high and was able to make it home all 50 miles on E lol... So anyways valvoline does great for me.

 

That's real interesting about the QT gas. That's who I always use too. I've got damn near all the same mods as you minus the Superchips (which I did have but sold). I'm getting 8.5 mpg. I don't drive very far to work so it's not as much a deal breaker for me as you, but I've just be resigned to not being able to get any better with this truck. I had an '01 a few years back and got 10 mpg. I'm of the mind that it's just that damn fuel thirsty 5.9.

 

Well as of today, my wife drove it this weekend about 400 miles round trip. When she got back she told me the truck was getting 11.1, I didn't believe her so I went and looked and sure as shit, it is! The next step I plan on doing is changing all the fluids and switching them to synthetic, But I'm not sure what to run. I have been thinking of using Royal Purple, but i don't know if I want to spend the money on it yet or not. I haven't herd enough good or bad to decided, well besides the guys on tv who get paid to use it, of course they are not going to talk bad about it.

 

Or just trade it and get a Chevy! My 1/2 ton 1988 4x4 with a tonneau cover gets 20mpg and that is with 373 gears and 32x11.5x15 BFG MT's on it. Yes that is mainly all hiway miles 120+ a day. As far as pulling I have 1 ton overloads on it, cam, roller rockers 700r4 trany and it will pull anything an mid 90's diesel will..... just saying....wish I could say the same about my newer dodge.:doh:
almost forgot the 20mpg is at 73 mph.

 

Everything you've listed should increase mileage with the exception of the chip. I am running a Turbo City intake, custom exhaust with headers, high flow cat (now blown :naughty, and the factory performance computer. The only downside to that is I have to run premium fuel. But I am getting 14 and that's running 3.55's and 35" BFG's at 6500ft altitude.

Two other things I'd try are: Maybe try running an oem type spark plug, I've seen instances when just plugs alone will cause poor performance and mpg. also I am not positive but I don't think spectre CAI are actually cold air intakes...if the filter is open to the hot air under the hood this would hurt performance over the stock intake. Need to grab cooler air from outside of the engine bay.

I've tried all different kinds of plugs and find the stock ones run best. Can't explain it, but these magnum engines love 'em.

Well I have an update My mileage has gone from 7.3 to 8.8, and the only thing that have changed is the gas I'm using. Since we moved recently I have quit using QT gas and started using BP, because it is right up the street. I have been reading that their gas is a whole lot better than QT. So that's a heads up for others to try. The other thing is we have gone from low 100 degree temps to mid to low 80's now. The next strep I'm going to take is changing the diff fluids and transfer case fluid. I want to do the trans but I don't want to mess up a working tranny with the way these dodges are lol. So... What fluids do you all suggest I use in the diff's and trans case????

The fuel we get here in Colorado, in a word, SUCKS!!! I run Shell or Safeway and that seems to get me the best results.

Well as of today, my wife drove it this weekend about 400 miles round trip. When she got back she told me the truck was getting 11.1, I didn't believe her so I went and looked and sure as shit, it is! The next step I plan on doing is changing all the fluids and switching them to synthetic, But I'm not sure what to run. I have been thinking of using Royal Purple, but i don't know if I want to spend the money on it yet or not. I haven't herd enough good or bad to decided, well besides the guys on tv who get paid to use it, of course they are not going to talk bad about it.

Royal Purple is good, but too expensive for me. I'm running Mobil 1 10/30 and am happy. When I rebuild my motor, I may switch to RP, but for now Mobil is cheaper and get's the job done.


BTW...newbie and glad to be here.

 

In an admittedly quick glance at the OP, I see several add-ons, but what about the basics? New O2 sensors, new MAP sensor? Timing chain tensioners can only do so much and wear out too so how about a new timing chain/ gear set?
The stock 5.9 cam is already pretty lazy, so once things get slack it just gets worse, besides, you need to shore up your foundation to make the most of the add-on mods. Also, how many miles on that cat? Free-flowing exhaust is useless with a clogged cat.

 

I agree you need a good running motor before moving on to mods, but I wouldn't start changing things without knowing they are bad, might as well just throw handfuls of cash at the engine bay. A bad sensor 9 times out of 10 will trigger a light, same with the cat. Timing chain or tensioner going bad should be noisy.