6.0 vs 6.6 on fuel mileage

matt78

Finally boosted launches
Sep 10, 2012
924
0
0
texas
I have a very good possibility of starting a service company with a few people I have worked with at various places now that I have my license for my trade. One topic that has come up has been a service vehicle. I am looking at 3/4 trucks,crew cab,with service beds. I am sticking with g.m.,and I really do not want used because I don't have time to replace shocks,brakes,etc.,well at least not in the beginning. Obviously I am a duramax fan but if the mileage difference on a 6.0 is not much the door is open for that as well. Also,how well do the 6.0 trannys hold up? This will be a truck that sees 30-40000 miles a year,alot of start stop driving , traffic,and highway. Any input is appreciated.
 

Dozerboy

Well-known member
Jun 23, 2009
4,916
496
83
TX of course
I have an '14 with a 6.0 for work. I get 13mpg on the road living in a metropolitan area. In the summer when my truck will idle most of the day I get 8mpg at best. I had a '15 Dodge 2500 with a a hemi for a loaner once it only got 6mpg in the summer. All of the diesel work trucks i had including the Duramax I got 17mpg or so on the road and 10mpg or better if idled all day.
I'm not crazy about the 6.0, but it seems to be holding up fine. Our plumber put the first 20k on it towing a mini hoe on a trailer all day. The trans does does get a little stupid about shifting sometimes. The fluid looks great, so I guess it's ok.

Sent from my SAMSUNG-SM-G900A using Tapatalk
 

hondarider552

Getting faster
May 28, 2008
10,627
2
36
34
Arizona
6.0 will have the 4L80 trans, maybe even the 6L90, not sure for 3500's.

You can buy a lot of gasoline for the 6k difference in price from a gasser 3500 than a diesel 3500. My vote is gas.
 

Awenta

Active member
Sep 28, 2014
4,090
2
38
CT
6.0 will have the 4L80 trans, maybe even the 6L90, not sure for 3500's.

You can buy a lot of gasoline for the 6k difference in price from a gasser 3500 than a diesel 3500. My vote is gas.
Yeah mine too. Plus downtime for emissions problems with the diesel.

That said I'd still buy the duramax

Sent from my SM-N910V using Tapatalk
 

PACougar

Active member
Jun 27, 2012
2,105
1
36
41
El Dorado Hills, Ca
I agree with Brian. You won't make up the difference in savings. However if you're doing lot's of towing then the diesel makes a lot more sense.
 

WolfLMM

Making Chips
Nov 21, 2006
4,005
26
48
38
AL
If it's 08 or newer it will have the 6l90e, pretty sure. Good motor good trans.
 
Jan 28, 2015
961
0
0
Ohio
Had a 6.0 before my first d max. Never had an issue with it besides the manifold bolts broke on the earlier ones. Truck had 190k on if before I sold it. Motor was original transmission lasted till 160 then needed rebuilt. 4l80e. They are just as reliable if not more then a 350 with some more power. Got decent mileage. 11-14 with 35s. The newer 6.0 vortecs are even better runNing motors.
 

Hoffie

New member
Mar 10, 2015
212
1
0
Far East LA - aka Phoenix
I talked to an RV transporter that has a 6.0 and he had 600k on the truck. The motor was original with no issues and he was on his 3rd transmission. I have 400k on my Duramax - original engine and transmission. We both are constantly pulling a trailer with the trucks. Maintenance is much lower price wise on a gas engine, repair parts are much lower and repair costs are lower. For example - Duramax head gasket replacement - $4k - $8k. Vortec 6.0 replace the entire engine for under $4k., and the transmissions are half the price of an Allison, as well.
 

Suge White

New member
Jul 4, 2016
11
0
1
Queen Creek, AZ
My 04 6.0 has 265k on it and runs like the day I got it. The mileage sucks but the maintenance is nil. I get about 13mpg but I idle a lot and spend all day in a subdivision turning circles. She still has no issue pulling my 10k toy hauler up nasty mountains in AZ heat when needed. LS motors love high rpm's so don't be afraid to wind 'em up. I had a very mild tune done to the engine and trans a long time ago that I'm sure helped the tranny live better and even bumped up my mileage a couple of mpg's. I'm new to the Dmax but it definitely gets better mileage. There's no way it would make up for the initial cost and maintenance costs though. As much as I love my diesel for a part time truck, I don't think I could justify it for every day use unless there was a permanently attached trailer with real weight on it.
 

02greysixer

Active member
Jun 4, 2011
1,829
7
38
North Central FL
I know of a few 6.0 vortecs that get treated like total crap. They're always loaded down and maintenance costs are pretty much non existent. I personally know of 2 05s that haven't even had a spark plug changed in 250k miles. They just keep plugging along.

Sent from my SAMSUNG-SM-G870A using Tapatalk
 

duratothemax

<--- slippery roads
Aug 28, 2006
7,139
10
0
Wyoming
Nothing wrong with a 6.0! No, its not going to tow heavy trailers like a Duramax, and its not going to get as good fuel economy.....but honestly in most other areas, its better.

-Oil changes are half as expensive
-Basically never have to change the fuel filter
-you can buy an entire good 6.0 short block for the price of one or two duramax fuel injectors
-the things just dont ever break
-you can treat them like crap and they just dont care

Ben
 

Al's max

Member
Jul 29, 2014
103
0
16
Texas
We owned a 2014 that never unhooked from a 6K pound trailer and would never see above 9mpg. Got as low as 6 before. This was always in town though. Put it on the highway and it would shift between 4th and 5th all the time. Never had any problems with it but we were glad to get rid of it for a Duramax!! Matt, we've got the best Duramax mechanic around!! Go with used.