About a month ago I got a AEM Brute Force air intake and a Magnaflow cat exhaust 2" pipe. installed on my '04 Quad Hemi. I was getting 11.7 city and 14 Hwy prior to the install. I havent changed my driving a bit an my millage is now 10.2 city 12.5 hwy. I was told that the intake and muffler would increase my milage by about 2 - 3 MPG. Running 89 octane.

Any ideas on why it dropped?

 

Thats interesting. I've only seen improvements on the mods you've done. I'm getting a consistent 2-3mpg better in the past year since I've done the same mods. Somethings that many people do not realize after certain mods is that they do drive harder because we all like to hear that CAI and exhaust roar. The other thing that I notice on my own truck that plays a huge factor is speed and wind. If I'm driving into wind, or its hitting the side of the truck, it knocks my mpg down 2-3 mpg all by itself. Also, I get better fuel economy @75mph than I do at 70mph or 80mph. I can't break 17mpg on the highway if I'm driving over 80mph.

 

I drove it like an idiot for the first week....It does sound good...and the power inceased was nice. But I cant figure out why the milage has dropped since.

 

reset the computer and drive the next week easy..

 

How do you reset it?

 

Thats makes a little more sence. Most likely the computer saw a new airflow profile, and re-learned how you were driving. So if you were driving like you stole it, then that might have had an effect on it. I'd reset the PCM and drive it for a few days nice and easy and see what that gets you.

 

How do you reset it?

 

I've done it on my truck, but the only way I can think of would be disconnecting the negative battery cable for some time. Try doing a "PCM Reset" search in the forum. I'm sure you'll find some good info.

 

just disconnect the neg battery terminal for a minute or so.

 

after you disconnect the battery, put the key in the on position for about 1 minute. take key out and reconnect battery.