I've heard different numbers from different mechanics. Some claim 60,000-65,000 miles, others 100,000 miles. Either way, you are overdue.

Don't worry about the downstream sensor (after the cat) unless you get a CEL from it. Just replace the upstream (in front of cat); thats the one that helps control your A/F ratio.


The EPA numbers, I find, are always stretched a tad from what your MPGs will actually be in real life. A company or two (I think the last one was Honda a few years back) have actually got in trouble with the EPA for stretching their math a little bit to much.

What kind of tires are you running? What size? Have you had your alignment checked?

 

I was down to 10 last tank so I threw in a can of seafoam in the tank and although its not empty yet, I can tell I'm getting better mileage. This is all in town, running the same daily routes as last tank. Just try something to clean injectors and it may help. All the idling and long warm-ups use lots more gas.

 

I have all the same installed components that you do (plus a supercharger, 60lb injectors,
and custom cut intake runners) and I've been getting 10mpg since winter began. I usually
get around 13-14 when the weather is good and I don't have to warm up the truck or run
it in 4wd. I doubt anything is wrong but I would take jason.w's advice and replace you O2
sensor. Its easy to change and has a great influence on how your truck runs.

 

You mentioned that you already have the air/fuel gauge, but haven't installed it yet. (Hopefully it is one that you can connect to a laptop and can data log the readings.) I would definitely do that as soon as you can so you can get those readings to Sean. He'll be able to fine tune the SCT programming specifically for your truck from those readings. I haven't spent the money for the A/F setup yet, but I will be in the near future. I really need to do it for mine, as I am getting close to the mpg that you are, but I know it'll be better after I get the data to Sean so he can fine tune it better. Since you already have spent the money for the stuff you need to do this, it would definitely be the FIRST place I would start!

I don't think you can compare the mpg on the stock tune to what it used to get as a stock truck. You've changed the way your truck "breathes" and the changes you've made may not be able to be fully calibrated in the PCM under the stock programming to give you the best fuel efficiency, not to mention power. There are of course other things that may be causing the lack of mpgs, but since you already have what you need to get the modifications you've already made to operate at their best, my suggestion is to start there. Then I would investigate further for any other potential issues.

 

Thanks to those of you who responded with informative posts. I'll check into the o2 sensor replacement and I'll get that gauge installed soon. The gauge is this one. http://www.glowshiftdirect.com/Blue-...el-Gauges.aspx

I doubt that I'll be able to do that (data logging) with this one and I just don't have the cash right now for a more expensive gauge. I tried Sea Foam a while back and I got damn near 17 MPG on the interstate at 80 MPH.

I've got the SCT tuner so would that be able to log the air/fuel readings?

EDIT: Oops, I'm also running the stock 265/75/16 tire size on the truck.

 

10mpg is all I get with my 318 4x2 living in Southern Mexifornia. Even with the highway drive from my house to NAS North Island, I only average 10mpg.


Sounds like your mileage is right on.

 

You have a 2 wheel drive Viper, you should be able to squeeze out atleast 11mpg,

 

I get better than Viper. I get at least 14.

Death Flash anyone?

 

I had mine up to 15, then I added SC 3815(from a hypertech PP3)the 1.7 RR's , put the 14x3 back on and relocated the IAT into it. And now I'm back down to 13.5 mpg. But, before any of the mods I have done, I was also getting 10 mpg.

 

yeah just for comparison i have the 318 im all stock and i get 13 in town 16 on the highway at 75-80mph , but around 11 in town during the winter