Type of gas

[ASU_Magnum]

Dodge recommends 89 octane fuel for the 3.5L. It says it doesnt recommend Premium...why not?

[Trouble]

Your question is 'why not'....Easy answer, it'll do nothing for the car. It was designed this way. The concept of octane ratings isnt that higher octane ratings are like putting magic in the gas tank, it's the ability to prevent detonation. If the car doesn't need it (usually based on the compression of the AF mixture) then it's not going to do anything for you. Now our cars are equipped with knock sensors so if you do run crappy gas which can cause minor detonation (pre combustion) then possibly, performance can be hurt though I'm not sure anyone has proved that our ECU's do indeed drop timing when knock count goes up. Now someone will likely chime in that higher octane gas has lower specific gravity and cooler burn temps etc. but to sum it up, there's no reason to go with 91/93 unless it's stated by the OEM.

-Trouble

[fnkychkn]

this TSB is a little old but i'm sure the same principles still apply:

NO: 14-08-97
SUBJECT: Poor Driveability With High DI (Driveability Index) Fuel
DATE: Nov. 21, 1997
SYMPTOM/CONDITION:
Long cold start times, warm-up sags, hesitations, and driveway die outs. These symptoms are most noticeable and severe at moderate ambient temperatures between 4 - 27 degrees C (40 - 80 degrees F).

DISCUSSION:
Gasoline with a high Driveability Index (DI) can cause the above described symptoms. DI is a measure of the gasolines total volatility, or tendency to vaporize completely. A high DI number is less volatile than a low DI number. Most premium gasoline sold in the U.S. has a higher (worse) DI index than regular or mid-grade gasoline. Use of premium gasoline is NOT recommended for vehicles designed to run on 87 (R+M)/2 regular or 89 (R+M)/2 mid-grade gasoline. High DI gasolines also cause higher emissions for the same reasons they cause driveability problems.

For vehicles that require an octane rating of 91 (R+M)/2, premium is recommended, or possibly required. Using premium fuel with a higher than recommended octane rating is not recommended. Owners who experience fuel related cold start and warm up driveability problems should try a gasoline with the recommended octane rating or different brands of gasoline until they find one that provides good performance.

The octane quality of gasoline is only a measure of its resistance to spark knock. The use of higher than recommended octane gasoline under normal operating conditions does NOT improve startability, idle quality, fuel economy, driveability, acceleration, engine durability, or emissions. In fact, most higher octane gasolines available in the U.S. have higher DI values than regular gasoline. Customers are most likely to experience poor driveability with premium gasoline than with regular.

Some vehicles, such as Viper, Prowler, 5.9L Grand Cherokee, 2.0L Turbo Talon, and 2.0L DOHC Neon have been specifically designed to take advantage of higher octane. These vehicles may have higher compression ratios, and/or more aggressive spark calibrations which provide optimum performance with the specified higher octane. However, other vehicles which are not specifically designed and calibrated to take advantage of higher octane will not benefit from higher octane.

Some vehicles may experience light spark knock in situations such as trailer towing or climbing steep sustained grades. Light knock or "ping" under these conditions is not harmful. However, if the customer is concerned about light knock under these circumstances, the use of 89 (R+M)/2 or even 91 (R+M)/2 premium gasoline may be temporarily warranted. If a vehicle is experiencing heavy spark knock on gasoline with its designed octane rating, this may be an indication of excessive combustion chamber deposits, or some other problem. Combustion chamber deposits can be removed with Mopar Combustion Chamber Conditioner p/n 04318001. Standard diagnostic procedures may help in identifying other potential causes of excessive knock.

Some gasoline marketers may advertise that their premium gasoline contains extra detergent additives. Under provisions of the Clean Air Act, ALL gasoline sold in the U.S. must contain effective deposit control additives. Nevertheless, if fuel injector or intake valve deposits are suspected of contributing to poor performance, occasional use of Mopar Fuel Injector Clean Up p/n 04549613 is a much less expensive way to maintain engine cleanliness than regular use of premium gasoline.

The attached charts (Figure 1 & Figure 2) show the negative effects of high DI fuel as related to customer satisfaction.

If fuel quality is suspected in causing a customers driveability concern, your zone technical office may be able to provide direction on procedures for fuel sample analysis.

POLICY: Information Only

[ASU_Magnum]

Cool, thanks for the info guys.

[BigBadMagnum99]

Right on Fnkychkn...thanks for that posting!

[blackcomb]

I've been torn between 87 and 89......

[SKINNI]

I HAVE AN R/T AND JUST FINISHED MY FIRST TANK OF PREMIUM. I ONLY GOT 235 MILES OUT OF THE TANK. USING MID GRADE I AVERAGE 250 MILES WHICH I THINK IS STILL ****Y. MY WIFE COMPLAINS THAT SHE WAS MORE SATISFIED WITH THE MILAGE IN MY AVALANCH...LOL. I LOVE THE HEMI THOUGH SO ILL DEAL WITH UNTIL THE LOTO COMES THROUGH AND I PICK UP THE SRT. THEN SHE CAN REALLY COMPLAIN

[BigBadMagnum99]

With just getting our 06 AWD RT Magnum, I have been very surprised and happy with our mileage with about 60% highway and 40% town avg. so far....and very difficult and I mean very difficult to baby that Hemi motor in town....lots of WOT.

We have been avg. overall 21 mpg (US Gallon). and getting about 375 miles/600 kms on a tank. At times on the highway I have seen upto 25 mpg. 65mph/105km/hr at a steady cruise. Around town the fuel mileage still is not to bad avg. about 16mpg (US Gallon) according to the EVIC. Both my wife and I are very pleased with the mileage.

The motor still has to break-in with only having just over 800 miles/1200km. I have been using 87 Octane fuel from Petro-Canada for our Magnum. This may drop with Petro-Canada bringing out there winter fuel blend.

[blackmagsxt]

I use 87 in my SXT and have since I bought it in July 2004, I get 25 miles per gallon. Almost all my driving is on highway.

[SKINNI]

With just getting our 06 AWD RT Magnum, I have been very surprised and happy with our mileage with about 60% highway and 40% town avg. so far....and very difficult and I mean very difficult to baby that Hemi motor in town....lots of WOT.

We have been avg. overall 21 mpg (US Gallon). and getting about 375 miles/600 kms on a tank. At times on the highway I have seen upto 25 mpg. 65mph/105km/hr at a steady cruise. Around town the fuel mileage still is not to bad avg. about 16mpg (US Gallon) according to the EVIC. Both my wife and I are very pleased with the mileage.

The motor still has to break-in with only having just over 800 miles/1200km. I have been using 87 Octane fuel from Petro-Canada for our Magnum. This may drop with Petro-Canada bringing out there winter fuel blend.

MAYBE I SHOULD TAKE MINE IN TO THE DEALERSHIP THEN. 16 MPG WOULD BE GREAT. FOR SOME REASON IM ONLY AVERAGING ABOUT 12-13 MPG AND I HAVE ABOUT 3500 MILES ON MINE.

[sstevens805]

Im at about 15, though i know that some of it is due to my heavy foot. One thing I do notice is that MDS doesnt come on very often, and when it does, it doesnt stay on for long. I drive (freeway) about 85-90 on long road trips (take lots of those). I cant get more than 300 out of any one tank, even using cruise control. I dont know why. Would leaving the battery cable off over night help, only mod I have is Magnaflow cat-back and never unplugged battery cable.

[GoofyTimL]

We have a 300C with the 5.7 Hemi. We're averaging 15-17 in and around town and about 275-306 miles per tank (we fill shortly after hitting 1/4 left... hardly ever get down to 1/8 left. On the recent Thanksgiving Road trip, most of the 700+ miles on the highway, the mileage varied from 22 to 24 mpg... depending mostly, I suppose, on slight slow downs due to slower traffic and poor weather in the Appalachian mountains between here and York, PA. Calculations are actual miles and actual gallons to fill. The EIC calc MPG is usually within 0.5-2 mpg of the actual calc.

We have used about four tankfuls of 87 (first month) and four of 89 octane (recommended for the "C"), and seen no difference at all in engine performance or fuel economy. Probably will return to using 87 octane based on this two-month experiment.

[ZMagnum]

I'm beginning to think that gas octane ratings are very inacurate. You might think you are buying 89 or 91 but what are you really getting?

[northeastern08]

I'm beginning to think that gas octane ratings are very inacurate. You might think you are buying 89 or 91 but what are you really getting?

I thought that was regulated somehow? I know there is a difference from station to station, but I did think there were limits in variation and octane ratings??

I could be wrong and making this up though...it is 1 in the morning and real and make believe start to come together around now :grin: dancing monkeys and elephants come at around 3 or 4...then the morning news at 5 and sleep by around 530...ohh alarms going off, its 6 time to get up love college life - papers, finals, and all kinds of funness to keep me going

-todd-

[mumzie]

I have tried the 87 and 89 octane fuels from Chevron with no noticeable differences. My mileage SUCKS either way. I did get the last tank up to 13 MPG.
I do about 65-70% in town - with a little bit of a lead foot - but not that much.

I have said it before - and I'll say it again - if the mileage doesn't start to go up, the R/T will be history. I wasn't looking for a high gas mileage car, but I would have kept driving my 97 Tahoe if I'd known the mileage on the magnum. The Tahoe got better mileage.