2006 Chrysler 300 Bad Gas Mileage

Tiny
DARRENDWILSON
  • MEMBER
  • 2006 CHRYSLER 300
  • V8
  • 2WD
  • AUTOMATIC
  • 19,000 MILES
I recently bought a 06 300C with 19k miles on it. On the highway I get about 20 MPG and in town about 13 MPG. On average for a typical week it gets about 14 MPG driving on highway and in town combined. I use to have an 07 SRT Design and it got combined over 17 MPG for the same commute. It doesn't get near the gas mileage the 07 got. The person I bought it from said the battery died a few times and I read online somewhere that it could take some time for the Multi Displacement System to reset if the battery dies. I'm wondering if there is a way to check if the MDS is working? Factory wheels and tires were P225/60R18 (704 Revolutions per mile) and the guy I bought it from put P265/35R22 (688 Revolutions per mile) which is about - 2.4%. I've also wondered if the change in wheels and rims would "throw off" the MDS and shift points. Any help is appreciated!
Sunday, May 9th, 2010 AT 11:22 PM

3 Replies

Tiny
2CARPRO JACK
  • MECHANIC
  • 11,533 POSTS
The wheel size will definitly make a difference in the mileage and performance. The trans shift points are gauged with the tire height as it comes stock, so taller overall height will change the actual engine rpm range that it is working in, which will change the mileage
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Tuesday, May 11th, 2010 AT 8:39 PM
Tiny
DARRENDWILSON
  • MEMBER
  • 6 POSTS
Do you recommend taking it to the Chrysler dealership and having the car's computer adjusted for the new tire and wheel size? It is pretty close as of now with the 688 revolutions per mile as compared to the stock 704 revolutions per mile.
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Tuesday, May 11th, 2010 AT 10:32 PM
Tiny
2CARPRO JACK
  • MECHANIC
  • 11,533 POSTS
I would have it reprogrammed. Also keep in mind the manufacturers make slight changes here and there from year to year to keep up with the EPA standards for economy, so almost every year will do a slight bit better than the previous. If you are going to take it to the dealer, may want to hit them up about any software updates for your car, since they are going to be in there anyway.
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Wednesday, May 12th, 2010 AT 8:13 AM

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