I have 1999 durango w/5.9 that I've put over 150,000 miles w/ no issues other than transmission. I get on average 16 mpg on regular. I'm looking at a 2003 durango r/t. What gas mileage should I expect? can I continue w/ regular gas? I'm not too much of a hot foot. Most mileage is two lane roads, 45 to 60 mph. Any info/ideas/opinions on durnago r/t would be appreciated. thanks/jcw

 

I have a 2000 Durango R/T. I am sure the 2003 R/T should not be much different. I am getting 12 city and 14 on the highway and that's with a light foot and travelling from 60-70 mph within the Texas state speed limits on state highways. That mpg was with a K&N air filter replacement that improved it a little. If I have no windy conditions, I can achieve 13/15. Gas mileage for the R/T's vs your regular 5.9 varies because one, all R/T durangos are running FULL TIME AWD. Two, R/T's come with higher gear ratio at 3:92, I assume your 5.9 regular durango problaby uses 3.55 or lower gear ratio. Three, R/T's REQUIRE 91 octane premium gas. But if you're always hovering around 45-55 mph speeds, I can see an R/T possibly getting 14/16 or up to the 17 possibly depending on external environmental conditions.

 

I have a 2003 R/T. Using premium gas would kill me and I really don't think it is necessary. I have always used regular gas and things have been fine. I get about 14 mpg city and sometimes 19-over 20 highway. I have put a Flowmaster and K/N filter and also that nifty little gadget you have probably seen on TV the Tornado. As long as your foot is light the Durango will be as light as it can be as well, lol.

Good Luck!

 

You're lucky that you are not experiencing any pinging or denotation using lower than "required" octane for your R/T. Also, I would love to get anywhere near what you get for gas mileage. You must live in a very flat area and drive below 55 mph to get those figures? I will never see 19 MPG on my R/T much less the rated 17 on highway. Then again I have not upgraded my muffler and still don't think those spacers will help because of the unique design of the 5.9 intake manifold. I'll have to experience some more to see what is making my MPG so low compared to yours.

 

Well do not think that you are alone. I should have said rerely over 20. I have seen 21 mpg on the highway and that is about all. I am just lucky that my R/T doesn't have to push over 2000 rpms to maintain 75 M.P.H. I live in a relatively flat area but it has its hills and such.

As far as the pinging and such- none what-so-ever. My father had a '99 Ram with the 5.9 and he used Regular throughout the 6 years he had it with no problem at all. I am not sure if our engines are different but I never had a problem. Did you experiment????

 

Now that is very odd. Your engine RPM's don't go over 2000 RPM's to maintain 75 MPH???? Two things I see here, either the 2003's 4 speed tranny is geared different especially with a much taller over drive gear, or your Durango is not running on 3.92 gears. At 75 MPH, my engine is running around 2200-2300 RPM's. My max speed is roughly 65 MPH at 2000 RPM's. That is my setup on my 2000 R/T.

As far as using Regular unlead on my R/T? Yes, I have used it ONLY ONCE. I would never do it again. I did it once only out of stupidity of miscalculating how much gas I have left to make it to the next fueling station and that fueling station did not have the premium 91 octane required by my R/T. The Durango just choked on that 87 octane gas. Luckily the fueling station had some 107 octane boost to raise the octane so my engine won't spit and sputter.

There are lots of Durangos and RAM's that uses the 5.9 engine and they run on regular fuel. Only the R/T models require the premium 91 octane because Chrysler re-tuned the computer programming more aggressively. Basically we gained an additional 5 HP and 10lbs of torque over a regular 5.9. Chrysler's computer tweaking required 91 octane gas for the additional gains.

Based on your statements, I hope you did not get a regular 4x4 Durango with a 5.9 and have the R/T's badging on it? I seen regular part-time 4x4 Durango 5.9's with lower gear ratios around 3.55 gears I think that can achieve those MPG numbers you mentioned.

 

LOL, no, the VIN has been pulled quite a few times! But at 70 I am right under 2000 RPMs. As far as the Premium octane debate, two dealers have told me the same that it was perfectly fine to use Regular. I have been using it for about 6 months with no problem at all and I am damn glad I am not having the problems that you guys are having because filling this up with Premium would be very costly!!!!

 

I hope someone can answer the differences on the transmission from the 2000 and 2003 Durango R/T's???? I would love to be hovering at 2000 rpm's at 70 mph!!! I can definitely see some MPG improvement there. Currently I am hovering around 64-65 mph at 2000 rpm's.

 

My 2001 R/T seems to be somewhere between you two guys... 2000 RPM's gets me just at about 70... I had my Speedo Calibrated by the Auto Club so I know it is accurate, I do not know how accurate the Tach is though... I thought maybe the overdrive was the difference but if I take that off I jump from 2000 to just above 3000...



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Card fan,

Looking at your pic, your are just above 2000 rpms at 70. Same for me. With my Needle directly on 2000 rpms, it rides on 64-65 mph. If it goes to 70, I will raise it up just little bit more, exactly at the position of your tach. As my gauges are the 2000 model which has an additional line spacer between the speeds, I would estimate my tach to be around 2100-2200 at 70 mph. 2300-2400 at 75 mph.

I'll take a pic of my gauges going at 70 mph at post it. My speedo has not been recalibrated so it just has the OEM settings.