Hey all, so I just bought a 2008 Hemi Aspen with MDS, tow package, lots of the options etc. 130k miles. I did replace the EGR valve (mopar) and got new spark plugs all 16 installed. (but seem to be getting the same mpg before that)

I've been concerned about the MPG.

The best I've been able to achieve is around 15.1 going 72 or so on the highway for 2.75 hours.

Before this I was on a faster highway for about 4 hours (in the same trip) going 77-80 or so. No major mountains etc. I wasn't towing anything I got around 13. This seems off to me anyone else?

Tires are nice Cooper SRX, all balanced and inflated to the proper psi. No noticeable alignment issues in the wheel. There is a very subtle/ slight vibration somewhere in the driveline I think when you go 67 to 70-71 or so. But the shop said the U joints look ok and the fluids are ok in the diffs. And the tires are in good shape almost new.

No check engine lights.

One thing I happened across in the manual is the "Fuel Saver" indicator should be on at times in the evic? I don't believe I have ever seen that come on. I pay pretty close attention to the vehicle also and how it drives and work on and diagnose a lot of my own vehicles and friends vehicles. I'm not sure I've ever noticed the MDS kicking in. Maybe a few times when passing on the highway but that also could have just been kicking out of OD.

So is there a way to confirm my MDS is kicking on? Any ideas on the slight vibration?

Thanks! And sorry if I broke any rules I'm a newbie

 

Also I'd like to add the MPG is done with a calculator not with the overhead. The overhead is pretty close to the same read out however.

 

Welcome to the Aspen club. The fuel saver mode should display on the EVIC if you have it set to read MPG. I leave mine set to this at all times so I can monitor the switch. I also hear the difference in the engine. However, I do have a Magnaflow cat back exhaust and AEM cold air intake so I can hear mine a little easier than the stock configuration.

I do have some issues with a couple of the MDS solenoids. Since you said you have no check engine lights this shouldn't be an issue for you. Even with my issues, I average around 15-16 MPG. Most of which is highway driving. Once while on a trip to Colorado while driving slow in the snow, I managed to hit 20 MPG. Didn't stay there long once I hit the mountains.

The MPG all boils down to maintaining a constant speed with minimal resistance from wind or hills. If you can travel on long flat surfaces, the MDS should kick in and the MPG should go up. If the fuel saver mode is not kicking in, you may have to get it checked out. Could be a code that is not displaying the engine light or could have been disabled by previous owner. I've actually heard of people doing this for some reason.

 

Welcome, congrats on the new addition.

I have an 09, and the Fuel Saver Icon was disabled for this model year for some reason. However, I was able to feel it kick in/out when on the highway. I have since disabled it, and really have not seen any change in MPGs. However, with that said, I don't do a lot of long distance highway driving, and I think that is where the big savings take place.

 

Thanks for the replies!

So is there a way beyond a tuner or tow mode to turn it on and off?

 

I think it stays off with Tow Mode, but I am not 100% sure on that. I used the Diablo inTune2 on my Aspen, with the 91 Octane Tune.

 

Dealer only type thing to check you think?

Yeah I feel like 16 going 75mph for 4 hours in a relatively flat route should be normal but when going 75 I'm hitting the 12 to 13 mark. I even made an effort to coast to stops, slow steady starts, cruise the whole way, etc. Strange.

 

I've also changed the air filter. I plan on trying to swap the o2 sensors. But it is incredible how hard they made getting to the wire harnesses on these aspens. Literally 1.5 inches of space for all 4. What do they expect you to drop the tyranny to change 02 sensors? I'm just going to splice the wires I can that I can reach and hope for the best with new ntk sensors.

 

I bought my 09 Aspen in April, and have recorded all the fuels stop in the Fuelly App since then. In that time, I have 18 fill ups covering 38xx miles, with an averge MPG of 14.4.

Best tank was 17.1 and worst 12.29.

 

I guess mine isn't too far off from that. Using similar app I've got 11 at the worse and 15.1 at best. Avg 12.8 over 3200 miles