I am considering the purchase of a black 09 4x4 quad cab hemi with 20's but am slightly concerned about the current fuel mileage people are getting. I am a chevy guy at heart and have looked into the new silverado's as well. I'm curious what you guys are averaging, both highway and round town. I have been watching the official MPG thread, but there are not many posted in there.

I have driven the truck twice, LOVE IT. Power is there, comfort is beyond that of my avalanche, and the styling is awesome! I'd be using this as a daily driver and on a lot of HIGHWAY miles. My avalanche with 4.10s is currently getting 18-19 highway and 12-17 average. I know you guys will say...it's a truck don't by it for mileage. Well, I need a truck and I'd like for it to get decent mileage. I'm not asking for 30 mpg, or a 24mpg average, just asking for decent fuel economy.

My other vehicle of purchase would be a vette. I have a beater already so that's taken care of!

 

They get an average of 17mpg to 18mpg, I have been hearing. Highway should be better. Get the 3.21's gears for sure. There is so much power that you really don't need the lower gears. They will pull better if you pull something, but hey you be blowing by people on the road with that higher topspeed. lol I would choose the 3.21's and go for it.

 

I have 09 4x4 crew cab. When if first bought it average 14.5 miles gallon now that im over 1000 notice my milage increased to 15.6 miles gallon. that is 50/50 driving.

 

I have a 4X2 hemi/3.55 with 20s. I have 5K miles on mine. At 65-70 mph on cruise, I get 20.5 mpg on the computer. I have not actually measured by pump reading at the station.

I do not agree with 5.9 on getting the 3.21 diff. With 20s, you really need 3.92. I bought a demo that had 3.55, but really wanted the 3.92. With 20s, you are only turning 1500 rpm at 70mph when using 3.21. It is not in the sweet spot for the hemi and will have to down shift too much. Mine is at 1750 rpm, but the 1900 of the 3.92 at 70 is smoother. The hemi is lugging at 1500 rpm.

The hemi is a great motor, but has some harmonic vibration at 1000-1200 rpm. It is glass smooth at 2000 rpm. Drive various rear ends and pay attention, you will see why I have come to these conclusions. Besides, you will see maybe .25-.5 mpg difference between the 3.21 compared to the 3.92. After you drive them, the 3.21 is much slower off the line than the lower ratios.

 

I am 16.6mpg average. I drive 80 miles round trip everyday to work on the highway at 65mph on cruise. I have the 5.7L Hemi and I do try to baby her. I do feel the 8cyl. kick off once I get going.

 

It will be way more of a noticable difference with the 3.92's on gas mileage then the 3.21's. Once you get in the city all the stop and go you have to be kidding me. 3.21's have plenty enough low end power. Still break the tires loose at a dead stop. There is a video on streetfire that my cousin will be downloading from this weekend.. One truck has 3.92's and the other has 3.21's. Both trucks are stock. The truck with the 3.92's got out in front almost a truck length. Once they reached 90mph the truck with the 3.21's was ahead and stayed that way.

The 20's aren't even bad on the truck. Buddie has an 08 Ram with 26's on it. Smokes them down like nothing. The 3.92's are just better for towing in my opinion. We are have opinions though.

 

You will actually use less gas in town with the 3.92. This is because you have to use less throttle to get the truck moving. As far as the 3.21, it is a dog down low when equiped with 20s. Not sure about your video, but with a governor limited speed of 105mph, your 3.21 is in no way going to catch the 3.92.

The purpose of my answer was not to debate one differential over another. I was just trying to share my knowledge and experience with the 09 Ram with a potential buyer so that he could make an educated decision. At least this will provide some info so that he can make his own choices. I will absolutely stand by my recommendation of not getting the 3.21 diff. You don't want the engine running at 1500 rpm at 70. The hemi is harmonically off and lugging at that rpm with that much wind resistance. If you look at the members of this forum that have the 09 Ram with 20s, almost all have the 3.92. There maybe a reason for that.

 

As for the gearing aspect. The lowest I would go with would be 3.55's. I was just kinda hoping for a bit better mileage out of the trucks. My 05 avalanche gets the same mileage and it doesn't shut down any cylinders. Sure it might not have 390hp, but it's never struggled to tow anything I've hooked to it. Keep the responces coming!

 

It was not my truck. None of them were. I haven't got mine past 70mph yet lol
I do understand what your saying, but I do not think the 3.21's are that bad. His seems to run fine with them.
105mph??? His stops at 110mph. It gets there quick but once you hit 105mph it smoothes out and stays at 110. I wonder why that is? Another question to find out about.
Either choice you make you can't go wrong. If the lowest you will go will be the 3.55's head to the dealer and see what they got in stock.

 

Hey Wait,
Chevy and Ford have always gotten about 2 mpg more that the Dodge. Your Aval. will get at least 2 maybe 3 better in town if you hotdog the hemi. It takes gas to make 400 hp.

5.9,
Mine shuts off big time at 106 mph. Maybe it shuts off early because it is climbing soooo fast, LOL. I am amazed at how fast and effortlessly this truck gets to 100 mph. It also feels much more stable at that speed than any pickup that I have ever driven. It feels like the truck would run 130-140 mph.