Purchased the 2005 R/T 2WD last week. Have put on 700+ miles, including at least 600 highway miles. Best long distance economy is 21 MPG (doing 60 - 75 MPH with AC on using Florida gas). Have seen 22 MPG in short stretches of 50-55 MPH, but no where near the 25 MPG I expected. Have tried both 89 and 87 octanes with no difference. I normally can get 26 MPG out of my 87 Vette, and 24 MPG out of my 99 Jimmy, so I doubt that the problem is "me".

Don't know if it will get better with time (doubt it), or related to the change in gas in Florida (and 3 other southern states) that was announced after Katrina hit, or do I have something actually "wrong".

I do feel the engine / trans "hunting" at speeds in the 35 to 50 MPH range. I normally would not expect this, and will talk to the dealer. Does anyone else feel this "hunting"?

But the performance is great!

Thanks,
Plasticman

 

I don't have the transmission issue. Your gas mileage will improve as you increase the miles on your car. Your highway mileage is GREATLY affected by how often the motor shuts down to 4 cylinders.

 

John, I see that you are in Hernando, I am in Ocala. Want to compare Magnums someday?


Bob

 

Plastic Man,
Try running 91 Octane and take a flat drive with the A/C Off and reset the Computer when you get on the Road. The computer will actually read a less than realistic MPG, so you don't run out of Gas as soon as you hit 0 Miles to Empty on the Computer Read-Out. If nothing works, you should still be happy with 21 MPG... My average is 14 MPG and I love it. Bet that Jimmy never drove like the Magnum, aye?

 

Thanks guys! Will try resetting it with the 91 octane.

Bob, yes we will need to "compare". Note that this is the wife's vehicle (but I drive it when we are together). She likes the power as well (use to have a Z-28, and after that an Avanti for 17 years, and then the Jimmy).

Was told by the dealer that the milage will get better at 5K miles (claimed it had an "E" chip that allowed for better break-in, but hurt milage - I have not heard that one before).

Jimmy, the 99 Jimmy was no Hemi! The Jimmy was totaled 2 weeks ago, so we needed a replacement quick. Magnum R/T was a great choice.

Plasticman

 

Im at 10K now and I get great mileage I think about what I get with my 88 vette. Its true about break in, after i got over 3000 miles, it felt like it had 100 more hp from new. My mileage has been pretty consistant since new, but I do lots of hiway driving. My trans also does a little bit of searching if its not under a load. So does my vette auto. I just lock it into a gear consistant with the speed. If im staying under 35- 40, i leave it in 3rd and if under 50-55, i leave it in 4th. I only use the drive (5th) when on freeway and not in traffic. I normally use 89, have used both 87 and 92 on occasion and dont notice that much difference in mileage or performance.

 

Plastic Man,
OK, you're right... I did notice some "Hunting" while trying to keep it at a steady 40-45 MPH. It's due to me not pushing it to the Floor or letting up on the Gas, as I usually do. I contribute that to me, as I am the guy who drove the car like that in the first place, to have the Computer 'Learn' my driving technique... Oh well...