I have a '05 1500 MDS hemi and I get what I think is horrible gas mileage. These motors are suppose to get better gas mileage but I only get at best 12 mpg in miami but up to 14 if in my hometown which has less stop and go traffic and only like 13.5 on the highway. I have a superchip for it but I don't know which performance level to set it on for the best results for all kinds of driving. I also have a magnaflow exhaust, throttle body spacer and k&n air filter. I was wondering if anyone else has this gas mileage issue for their MDS and if theres anything to do to help the mpg or if there is nothing I can do about the gas mileage and have to deal with it. Thanks

 

First of all, if you have an '05, you DON'T have MDS. It's an '06+ feature for 1500s (non MegaCabs). Secondly, the TB Spacer is doing NOTHING for performance and is in all likelihood throwing the O2 at the TB off a tad, causing a slight loss in fuel economy. This item is beneficial in early (late '80s - early '90s) throttle body setups but should not be used in a modern throttle body.

12-14 is pretty much the average for "in-town" use from a 350 HP V8 engine in a 5500 lb. truck. But your highway average is down a tad, should be more like 16-18 if your driving habits are good.

I find I get the best fuel economy with my Superchips on Performance with 93 octane gas. The increase in MPGs offsets the added cost of the higher octane fuel.

Proper maintenance is the KEY here. Plug changes at 30k miles, fresh filters and synthetic lubes everywhere you can use them. A dirty throttle body plate and worn EGR valve are prime MPG robbers and often go neglected. The throttle body should be cleaned at least every 30k miles and the max I let an EGR go without replacement is 50k miles.

Tire air pressure can also be a bad culprit, as running just 5 lbs. light can steal 2-3 mpgs. I like to run my tires at 80% of the maximum cold PSI listed on the side of the tire.

My pig weighs in at close to 7000 lbs. and runs 35" tires and I'm close to where you are, about 11-12 in town but I can about nip 16 on trips if I keep it around 70 mph...

 

I have the '06 MDS but some of the truck parts say '05. i don't know why they made this motor if you get the same mileage on your truck thats not a MDS

 

First, is it a quad cab or reg cab? 2wd or 4wd? Running big tires and a lift or lowered on lopro tires?

Second, bump the tune in the superchips to the 91 and turn off the MDS (difference between 91 and 87 on a full tank of gas, at least here, is less than the cost of a hamburger and fries so no reason not to be running it). I have yet to hear anyone with the MDS say they get better mpg out of their truck with it vs off.

Third, what gears do you have? 3.55? 3.92? or did you replace them for something larger like 4.10's or 4.56's?

Hammer pretty much hit everything on the head though about the maintenance.

 

And as Hammer said, the mileage you are getting is pretty much what everyone else is getting for those years.

I think the only thing Hammer missed was the add-on of an electric fan swap and air filter

 

Its 4wd regular cab with no lift or big tires. I just changed the superchip setting and ill see how it goes. How do you turn off the MDS?

 

Read the first sentence of Hammers post in post #2

 

What? Why would I read his first sentence? I have a MDS motor.......

 

Sorry I missed your post after that about having an 06 engine.

Are you absolutely sure?

The mileage you are getting is good IMO. I get maybe 11-12. But IF ou want to disable it then you would need a tuner like Superchips or Diablo

However, im sure you know MDS was designed to be a fuel saver. With that being said, there are plenty of threads both agreeing to and disputing this.

 

Believe me i have that dam MDS motor, it gets annoying when the motor is using 4 cylinders and you try to pass someone or speed up the reaction is delayed and the engine cranks up couple thousand RPM's and jerks the whole truck.

I have a Superchip but do you know if its bad to turn the MDS off in the truck? I feel like it might mess up the trucks computer.