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I just took my '09 RAM in and had the dealer perform a tune up, fuel delivery system service and misc. maintenance. Since the dealer performed service my highway mileage went from 20mpg to 15mpg and my in town mileage went from 16mpg to 12mpg. Spoke to dealer and their response was "none of the work performed should effect your mpg". Personally I though everything they did could potentially effect the mpg! Unfortunately they aren't offering any assistance and my mileage appears to be getting even worse. Last checked my hwy. mileage was down to 13.8mpg. Has anyone experience a similar scenario or does anyone have any suggestions as to things I can look into myself or suggest to the dealer?

Total work performed:
Synthetic Oil Change
Tune Up
Fuel System Service (clean, flush, etc.)
Front & Rear Differential Service
Transfer Case Service
Auto Transmission Service
Tire Rotation & Balance
Steering Alignment
 
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Interesting turn of events. I would never have thought that the mileage would suffer from those services.

One question...how are you measuring the mileage? Using the vehicle computer? How long have you been measuring the mileage since the service?
 

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Had a vehicle do that to me before. long time ago. It was a loose spark plug wire, not making a great connection. It could be something as simple as them shortsheeting you on a quart of oil. Is is running any different?
 

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Had a vehicle do that to me before. long time ago. It was a loose spark plug wire, not making a great connection. It could be something as simple as them shortsheeting you on a quart of oil. Is is running any different?
You'll have to explain how being a quart low can cause poor fuel economy. I must be missing something.
 

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It is possible they reset your evic and your average fuel mileage is now based on much shorter distance? I think thats the only thing that makes sence.
 

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Discussion Starter #6
I've checked the plug wires, oil & trans fluid. I went back to the dealer a second time and they state that they do not reset the ECM. Even if they did I've gone through four tanks of gas now and it seems to actually be getting worse. Thinking that the mpg calculator could be wrong (not that it was before) I've been doing my own math at the pump. Right now I'm down to 14.7 on the hgwy!!!
 

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My mpgs have gone down a little now with the winter fuels...about 1-2 mpgs.

What exactly did they do for the "tune up" portion?
 

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i just turned 36,000 miles & had the spark plugs changed & new K&N air filter
my highway mileage went from 15.8 MPG to 17 & sometimes 18 MPG,
it now has way more power than brand new & the Magnaflow muffler even sounds better than before, it has been on the Ram since i had 700 miles on it. The sound when i downshift when coming to a stop, makes me grin.
it now feels like the Ram has some sort of an ENGINE BRAKE when i am going down a hill & take my foot of the throttle.
I know that they had to do some kind of a computer flash to make such a dramatic change
 

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Few things come to mind here.

1. What exactly does "tune-up" encompass according to the dealer? Just curious.
2. I don't waste my time checking mpg in the winter. Gas additives at the pump required by cities and states, longer warm up times, high idle longer than in the summer, bad road conditions, etc, etc, can all add up to lousy mpg.

3. I never trust the EVIC because it averages mpg over the entire run since the last time it was reset. Its a neat toy and that's about it in my mind.
 

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they probably reset your adaptives.....some drive time and it will relearn and youll be back to normal......just a guess!
 

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Prob has nothing to do with what is going on with your truck but I put fuel injector cleaner into my 09 recently and my milage went from 16-17 hwy to 14-15...I've even seen 13. All of this is according to the computer. I have yet to add it up via the ole' "how many miles have you driven with how many gallons of gas you put in" method. Everything is running fine on my truck as well. Not sure what the deal is. Not impressed though.
 

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i would try resetting the computer to base perameters. sometimes when you alter or more systems it doesnt fit what the other systems have learned. take both battery cables off and hook them together for say 30 seconds. that will reset everything back to new and match the new components that were installed. then lets see what u got.
 

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I found out that sometimes when you use your automatic starter in the winter for say 15-20 minutes before you go to our vehicle, it brings your MPG way down! I figured thats the reason mine dropped from 13-14ish to 11-12 ish. Just a heads up
 

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Hemilancer: What does resetting the base perameters mean? I guess I should ask what does it reset? I understand it will reset the computer but does that mean I have to reset my seat settings and my garage door opener? Just curious before I try. thanks for the info.
 

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engines learn bad habits like how to run with worn plugs or a dirty throttle body. when you reset the perameters you erase all those bad habits its learned and start fresh like when its new. and yes u will most likely lose all your other settings.
 

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engines learn bad habits like how to run with worn plugs or a dirty throttle body. when you reset the perameters you erase all those bad habits its learned and start fresh like when its new. and yes u will most likely lose all your other settings.

yes.....its all about adaptives.....the good news is that it will relearn......
 

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One other thing you can try is see if your leaking air on the intake. If they changed the air filter make sure nothing came loose all the way to the throttlebody. Lastly you can try some fuel injector cleaner. What another poster said about the truck learning bad habits makes sense. Thinking about it your new tune up parts could be different and the truck isnt tuned right now. Are you sure they used the right parts? meaning especially the spark plugs did you check the gaps? I do my own maintenance and often see plugs made for my engine off actually I see this for all my vehicles especially my motorcycle. This will certainly effect the way your engine burns fuel. I read somewhere that hemi trucks are REAL picky about which kinds of plugs they use. I have a buddy who works at a dealership and he tells me when they run out of certain items they just make up the difference with the wrong parts and just change the gaps. This is one reason why I do my own maintenance when I can I dont trust any service company. Last oil change I caught them not changing the oil filter or rotating the tires as promissed (I mark my tires and oil filter for proof). Its all profit for the dealer.
 

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I've got the same thing going on since I did my own tune up with factory ngk's. Everything down 4-5 mpg's in the 1000 miles since. I'm gonna go back through everything and double check but no codes so I doubt it will help.
 
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