Not too far off, but if you do drive a lot of highway, I'd want to see that number up a little higher if I were you.

Anything else to consider? Is the Aspen leveled (front lifted a little to match the rears), or are you running a larger than stock OD tire?

One thing I didn't consider as well, is that the 2009 5.7 is a little different than the 2008. I'd have to look up the MPG numbers stated by Chrysler.

 

07/08 have 13 city 18 highway.
09 has 13 city 19 highway.

(5.7 4wd)

 

So they made probably some slight improvements. Tires are the same as size as stock yes. Do you have the 3.55 or 3.92 axle? I've heard the 3.55 is better for mpg?

But yeah those are my thoughts exactly I should be getting around 14 for an average. I'll have to keep picking at little things to see if I can improve it.

 

I have the 3.92 with the Tow Pkg as well, and I am running 265/70/17 Nitto Terra Grappler G2s. Stock tires were 265/50/20 (30.43OD) and the 17's I'm running are 31.61OD.

3.55 would be better for MPG, correct. It'd be less RPMs at cruising speeds.

 

Yeah same here. But I still have the 20s for the tires.

 

The 20" wheels look great on these trucks, but I really like the softer ride of 17/18 wheels.

I got a killer deal on some Ram Rebel Black Edition wheels for $300 on Craigslist and then bought the Nitto Tires at Discount Tire for $500 ($600 - $100 rebate), and then $100 to install. So the whole setup cost me roughly $900.

Then I sold my OEM 20" wheels one by one on Ebay for $200, $180, $275, $204 ($859 total) and sold the tires that were on those wheels on Craigslist for $300.

All in all, up a few bucks after shipping and ebay/paypal fees.....and my body enjoys the squishy ride.

 

Nice!

 

themps, it sounds like you and I basically have the same setup. 08' AWD, 5.7L, 3.92 rear end with tow package. I am running Michelin 265/60 R18 tires. Like I said, I typically run around 15-16 MPG. Mostly highway. However, I typically run around 75-80 and I often get in to the throttle to pass people. I loose most of my MPG while traveling down my private rock road of about 1/2 mile due to the fact that I'm idling all the way to reduce dust.

If you are not seeing the "Fuel Saver" pop up on your display, it may have been disabled. Like Rawyzf said, he disabled his with a tuner. If you can get access to one of these you can check this. Otherwise it's the dealer. And yes, if tow mode is enabled it will disable fuel saver mode.

A couple other things to consider. Make sure you are running the correct oil viscosity. The MDS is picky about running the recommended 5w-20. If you run a thicker oil, it can cause it to fail. Also, don't run the cheap gas. I found running 89 octane gives better fuel mileage than 87.

 

Yep same one. I've got about 133k miles on it.
Running Pennzoil HM Full Synthetic 5w20. I ran 89 for a while but it didn't seem to help and 30 more per gallon for some extra HP seemed didn't seem worth it at 13 hwy mpg. But I might got back to it the math makes sense.

But it does seem like my MDS is off somehow. I just hope I didn't buy it broken somehow (seems like a check engine light would be on either way though?) Can these same tuners turn it back on? I'm assuming yes. Wonder if it would be worth taking to the dealer or buying a tuner might end up being the same price lol.

I just changed one of the upstream o2 sensors today before it started raining. Gonna finish the other another day. The downstreams don't do anything for mpg so I'll probably leave those given how hard it is to access the sensor and wires. Just hoping my wiring holds up under the weather.

 

If their is an issue with the system, you should have a check engine light on. I have two solenoids acting up and I get a engine light. Now if the system is disabled, this should bypass the engine light. Rawzf would have to confirm this since he said he has his disabled. I've got to say, at this point I wish I could disable mine. Since I do have the check engine light on due to these solenoids, I will not be able to pass inspection next month when it is due. Even though the MDS is not technically emission related. A check engine light will fail inspection. At least here in TX.

If it is disabled due to a tuner, it should be able to reset back to factory default with a tuner. Those Diablo tuners are not cheap though. $330-$600 depending on which one you go with.