5.9 or 6.7 Cummins

[Montauk17]

I am about to purchase a one ton to work out of and can't decide to get a newer 6.7 or try to find a low mileage 5.9. I know the 5.9 is proven and gets better fuel mileage. Guy we hunt with has a 5.9 and I rode with him to the camp a few weeks ago the truck got 25mpg with the cruise on 70. What can I expect to get with a 6.7? How much does removing the DPF help with mpg on the 6.7? Any info would be helpful.

[Andy C]

5.9 all the way. I have had 3 6.7 dident like any of them!!! got a 4wd dully with a 6 speed and only get 16 to 16.5 on a good days. theres a guy in Bryan Tx. putting in new 5.9's in place of the 6.7 thanking about haveing it done.

[Bucoo]

My buddy has a 6.7 dually automatic with grip tires cruising at about 60 he gets about 21-23 (deletes with edge). Dad has a 6.7 standard and going about 75 on the interstate with 35s he gets 19 or so without deletes. My brother has a 6.7 with 35s also with an automatic and gets over 20 mpg cruising on interstate and has gotten 25 mpg before (deletes with smarty). Either way you go ought to be good.

[whunter29]

Well I have had a 07 with 6.7 the truck got 18mpg with a automatic an 410 gears. I deleted the egr and emission on it at 220000 miles. That was my only complaint with the truck besides the poor fuel mpg when pulling. I sold the truck with 300000 miles and its now got 400000 on it. I now have a 11 5500 with 87000 miles on it with no problems at all.

[weedeater]

Buy you a 5.9 in a 05-06 if possible, I had an 06 3/4ton and it was a great truck but in 07 they changed to new 6.7 and have heard a lot of bad trouble with it.... that's just my opinion and what I heard

[Fishmaster19]

The 6.7 has fuel system issues and turbo issues. I dont care what anyone tells you, there is not a truck on the road with stock tires or big tires programmer or no programmer delete or no delete that is gonna get over 20mpg! If it does then they must have put 20k under the hood...and where is the savings in that?! the 6.7 shoud get around 17 or 18 on highway and the 5.9 will get 22 at 60 to 65 mph. go to 70 and itll get down to 20 or below.

[Bucoo]

Originally Posted by Fishmaster19

The 6.7 has fuel system issues and turbo issues. I dont care what anyone tells you, there is not a truck on the road with stock tires or big tires programmer or no programmer delete or no delete that is gonna get over 20mpg! If it does then they must have put 20k under the hood...and where is the savings in that?! the 6.7 shoud get around 17 or 18 on highway and the 5.9 will get 22 at 60 to 65 mph. go to 70 and itll get down to 20 or below.

So you saying I'm lying? What makes you the expert?

[Montauk17]

I witnesses first hand a 5.9 2500 4x4 crew cab long wheel base getting 25mpg with the cruise set on 70. Stock size tires and a edge programmer. I hear alot more issues with the 6.7. I found a 5.9 with 70k miles but it is in houston. Gunna keep looking or I may drive to houston it is super clean. Thanks for the info

[whunter29]

Originally Posted by Fishmaster19

The 6.7 has fuel system issues and turbo issues. I dont care what anyone tells you, there is not a truck on the road with stock tires or big tires programmer or no programmer delete or no delete that is gonna get over 20mpg! If it does then they must have put 20k under the hood...and where is the savings in that?! the 6.7 shoud get around 17 or 18 on highway and the 5.9 will get 22 at 60 to 65 mph. go to 70 and itll get down to 20 or below.

I have never had fuel system issues on my two 6.7s and all of the turbo issues that I have heard about were the direct result of the clean burn exhaust system malfunctioning. I can tell you this my dad has had both the 5.9 and the 6.7 and the 5.9 gets better mpg but doesn't have near the power of the 6.7 stock. Now when he put an H&S tuner on the 5.9 it helped it some but it still won't run with the stock 6.7.

[weedeater]

I won't agree or disagree about the fuel mileage numbers but I know for a fact that putting mine on 65mph cruise control it would SHOW 25+ but when I would calculate mileage and gallons it was about 20mpg and running 75mph to west Texas it would show 22-23mpg but calculate to about 18-19mpg.... this was over several trips and several yrs on a completely stock 5.9 3/4 ton 4x4

[whunter29]

Also on the fuel mileage debate going on never trust the lying mpg on the truck because I can guarantee you are getting from 1-5 mpg less than its showing you and I have proven this fact to many people by simply calculating mpg the old school way.

[meaux fishing]

Anybody got a programmer for a 5.9 I can use? I want to see if I can improve my mpg. I got a 6 speed dually and I'm lucky to get 16. Maybe I just have a low geared rear end. It will pull a loaded 24 ft trailer full of 400lbs calves and accelerate up a hill with out straining though

[Fishmaster19]

The mpg shown on the dash is ALWAYS off! I even read a news article on it a few months back. They are on average, from any given manufacturer, off by 5 - 18%.

[DA COVE]

Originally Posted by Bucoo

My buddy has a 6.7 dually automatic with grip tires cruising at about 60 he gets about 21-23 (deletes with edge). Dad has a 6.7 standard and going about 75 on the interstate with 35s he gets 19 or so without deletes. My brother has a 6.7 with 35s also with an automatic and gets over 20 mpg cruising on interstate and has gotten 25 mpg before (deletes with smarty). Either way you go ought to be good.

Yea, This is my truck 6.7 Mega cab 4x4 w/ 6spd on 35" toyo's.. Staight highway, it'll calculate 19-20. Have got 22 calculated on a trip to dallas on 33s. Not overhead.. 10-12 pulling 35' camper running 75 also.. Bone stock. Oh yea, I have a fairly heavy foot..
Delete it and u'll have more power and just as good mileage as the 5.9. And there's more low mileage 6.7s out there than 5.9s.

[DA COVE]

Originally Posted by Fishmaster19

The mpg shown on the dash is ALWAYS off! I even read a news article on it a few months back. They are on average, from any given manufacturer, off by 5 - 18%.

Do u have one?? Or did u read that too??

[Fishmaster19]

The one in my 09 f150 always shows about 2 or 3 mpg better than when i calculate it myself as did my f350 and all of my friends and families vehicles.

[Fishmaster19]

Originally Posted by Bucoo

So you saying I'm lying? What makes you the expert?

My bad man I wasnt trying to offend anyone. But I have had a diesel and have many friends with them and a few of my friends are diesel mechanics so I am speaking from my own experience.

[rustyb]

I just got rid of my 6.7. I loved the truck but the fuel mileage sucked. It really sucked towing. 11MPG It was bone stock. I had the 5,9 before and it was awesome on fuel. Cummins are awesome. I dont think its a 5.9 versus a 6.7 thing. I think it is the newer 6.7 has all that pollution crap on it. Finding a low mileage 5.9 may be tough.

[wtretrievers]

I've got the 5.9 2006 4wd quad cab & have put all 175k on it. Still runs just like the day I bought it. I'll get 21-22 sometimes 23 on interstate 60-65 hit 70 & it starts dropping fast. It'll tell me I'm get 25 mpg but caluculations tell me 22 or so. I have a LARGE AFE Filter, no cat & 5" magnaflow exhaust from turbo back & a programmer. Each of these items jumped my mpg by 2-3 mpg. Ticket with a diesel is to let it breathe! What air is going in must go out! Sitting in my truck at idle I can hear the air going thru the intake.
The 5.9 is a stud. I know there was a few bugs with the 6.7 on the polution crap. But don't think it was anything major

[Shallow Runner]

I personally own a 2012 ram 2500 4x4. I love it. Way more power than the 5.9. I get 16-17mpg.hwy and 14.5 around town. My truck is bone stock. My brother has an 07 ram 2500 4x4 deleted with 33's he gets 21mpg average. My uncle had a 2012 ram 3500 4x4 and the front end broke 3 times on him. This is something I hear has been a problem on all the new 6.7 3500's. don't take my word for it though, look it up. Personally I love my 2500 but I wouldn't buy the 3500. IMHO.