8.1L vs. D-max

Roofer · November 14, 2001

What have you guys with 8.1L been getting for mileage? My buddy's dad has a '02 2500HD CC sb, and he says he is getting about 9 mpg empty and about 5-6 pulling his snowmobile trailer. I think that is horrible for the 21st century. Trucks back in the 70's were getting that mileage with a 400ci.

What about the diesel? What are you guys getting for mileage? I want a new truck, but I don't wanna cut my mileage in half. Is the D-max as good on power and mileage as GM said it would be?

Shaners · November 14, 2001

I've been hearing 10-11 in town and 13-14 on the highway. The problem is you have to learn not to use all that power when you don't need it... (I know that would be hard).

The only Dmax owner I know has a crewcab dually 4x4 with the Allison auto. He bought the truck in Chicago, and averaged over 19 mpg's bringing it back home to PA.

pacodiablo · November 14, 2001

dmaxes are nice, but they are $5,000. if you add an alli that goes to about $7,000. a BB will cost less when buying the truck, but MPG is not as nice. anywhere between 6 and 14 MPG w/ 8.1

viperapex · November 14, 2001

I have about 1500 miles on my rig now, and I'm doing about 9 mpg in town and 15 on the highway. Going to add a FIPK GII and hopefully gain between 1/2 and a full mpg. Like Shaners said though, It takes a strong will not to mash the accelerator. This rig will pick up and move if you want it to. Anytime I start worrying about the MPG I just stomp on it and I'm ok again.

Hope this helps.

Sean

raventai · November 14, 2001

I have the 8.1 and it is a strong engine and it is a gas hog but it is almost 500 cubes (496 cid)so it is suprizingly efficient

I am getting about 10 mpg now I got the gas instead of diesel because I do not like the fumes, noise, and lack of "punch" eaven thow the diesel has more tourque it dose not have the respose of the gas

if u will be pulling heavy loads a lot the diesel is the way to go

tbyrne · November 14, 2001

Stop asking the Dmax guys what their mileage is! It gets depressing

I see between 6-8 while towing a 24' enclosed car hauler with my 6.0 and am hoping to get close to 10 while towing with the 8.1. I talked to someone that used his 8.1 to pull a 32' trailer and he was getting 9 MPG.

Tom

2001 Supercharged 6.0 Suburban- for sale! -15.87 @ 88.41

2002 8.1 Suburban - coming soon!

FIRECAT · November 14, 2001

My brother (8100HD) is getting about 12-14MPG with his 8.1. His friend is getting about 9-10 with his Duramax. I have had the opportunity to drive both of these trucks and prefer the 8.1. I have driven them loaded and unloaded. The 8.1, towing about a 6000lb trailer easily pulls hills better than the duramax with a similarly loaded trailer. The difference that I saw was that while the Duramax pulls well, and maintains speed fine, the 8.1 will actually accelerate uphill if you want it too.

Another quick story, My brother's 8.1 and my 5.3 got the same mileage, on the same trip, towing identicle trailers!!! We both had filled up together and were traveling together, the low fuel lights went on, within a 1/2 mile of each other. From what I can tell, the 5.3 needed to work extra hard to maintain the speed and tow the load, while it was like "No sweat" for the 8.1. I am sold and hopefully will be getting a 8.1 HD or AV next year!

If you guys want more info, call out to 8100HD, I'm sure he'll respond.

FIRECAT · November 14, 2001

OH, BTW, Both of our trucks have the 3.73 rears.

Roofer · November 14, 2001

Quote from FIRECAT, posted on Nov. 14 2001,4:56

My brother (8100HD) is getting about 12-14MPG with his 8.1. His friend is getting about 9-10 with his Duramax. I have had the opportunity to drive both of these trucks and prefer the 8.1. I have driven them loaded and unloaded. The 8.1, towing about a 6000lb trailer easily pulls hills better than the duramax with a similarly loaded trailer. The difference that I saw was that while the Duramax pulls well, and maintains speed fine, the 8.1 will actually accelerate uphill if you want it too.

Another quick story, My brother's 8.1 and my 5.3 got the same mileage, on the same trip, towing identicle trailers!!! We both had filled up together and were traveling together, the low fuel lights went on, within a 1/2 mile of each other. From what I can tell, the 5.3 needed to work extra hard to maintain the speed and tow the load, while it was like "No sweat" for the 8.1. I am sold and hopefully will be getting a 8.1 HD or AV next year!

If you guys want more info, call out to 8100HD, I'm sure he'll respond.

Well that just blows my mind! How can a Diesel get worse mileage than a big block? Our F550 PSD weighing in at about 12,500 empty gets 10 or better, even when hauling. Don't get me wrong, I believe you, but it's just hard to believe. Maybe the diesel just needs to put on a few more miles before the mpg goes up.

Kansas Kid · November 14, 2001

Quote from Roofer, posted on Nov. 14 2001,5:23

Don't get me wrong, I believe you, but it's just hard to believe. Maybe the diesel just needs to put on a few more miles before the mpg goes up.

I'm in the same boat as you Roofer. With my cousins F350 PSD we regularly tow a gooseneck trailer loaded with hay at a GCWR of 25000lbs. The truck always gets 10-11mpg, an thats not driving it easy. I'd really have to say there is a major problem with that Duramax to only get 9-10mpg unloaded.

As for the original question, I think it all just comes down to a matter of preference. I've driven both, with both available transmissions. While the 8100 was faster unloaded and will probably be faster in some situations loaded, I still like the Duramax better. When you start pulling a trailer upwards of 10000lbs, the bigblock is going to be working alot harder then a diesel. I guarantee you that with the loads I pull, the 8100 would have to screem along at 4500rpm plus to pull worth a crap, where the diesel will happily pull at about 2300rpm.

And on a final note, if you start to seriously consider getting a new truck, do yourself a favor and test drive a 6-speed behind either motor. That Allison sucks up alot of power (and probably 2-3mpg) and you will definitly notice the difference. I know I wouldn't want an Allison after test driving the two with a 6-speed.

8100HD · November 15, 2001

I to am amazed but my buddies Dura is getting no better mileage than my 8.1. He's running 265's but that should not make the difference. He has about 6500 miles on it now and said that if he doesn't see better hes going to get an 8.1. I get to drive both all the time and we both trailer similar loads as my bro stated, and all three agree that maybe with heavier than 10k lbs loads the Dura might be better but from there and below the 8.1 simply rips. But to be fair I do have a Jet PCM in my truck, it made a difference, maybe more than I thought. Just my $.02.