Having been in a similar situation (see signature below), I’ll share what I found out when I did my upgrade.
For the 3000# trailer, any combination would do fine, but the 7000# trailer is another story. The 6.0/3.73 combo would be marginal for 7000#. The 5.3/3.73 combo I had was not enough for 7000#, and the 6.0 doesn’t have that much more power of the 5.3 to make a huge difference. (For 2000-2003 models, the 5.3 puts out 285 hp and 325# torque while the 6.0 puts out 320 hp and 360# torque and the 8.1 puts out 340 hp and 455# torque. All numbers went up slightly for 2004.) A better combination would be the 6.0/4.10, at least until you look at the gas mileage compared to the 8.1/3.73 which I found gets slightly less city and freeway, but about the same towing.
In my current Suburban, straight freeway driving, I get 13-14 mpg depending on speed. Around town, 11-12. towing, 7.5-8. All using regular unleaded fuel. Haven’t tried using the higher octane stuff to see if that would make a difference or not, but the price…would it be worth it? Don’t know.
Between my current and former Suburbans, it’s like night and day! Hardly notice the trailer back there any more unless the tranny downshifts out of OD.
Probably the biggest difference between your truck and the Suburban is payload capacity. Don’t believe the published numbers! As you can see in my sig, my current truck weighs 6700# fully fueled leaving me with a true payload capacity of 1900#, not the 2487# published in the sales brochure. Same truck with a 6.0 instead of the 8.1 weighs about 300# less. Ask the dealer what the delivery weight was for a particular truck and you’ll get a good picture of what you’re up to. If the dealer can’t tell you, go get it weighed. Do the math and make sure you stay under GVWR. Probably won’t be a problem with GCWR, but wouldn’t hurt to check anyway.
Get the 8.1/3.73 combo and you won’t be disappointed!
Wow! What a response! Yes I would love the 8.1 with 3.73, but since it will spend about half it's life as an almost daily driver, mileage is a concern with the 8.1.
I am just curious how you are able to get better gas mislege with a 500CI motor and 3.73 then I am with a 360CI and 4.10? Did they just improve the motors that much?
What I also find interesting is the huge variation in the MPG with towing/ city/ highway versus mine the gets 10mpg almost no matter what. Opinion? Great site by the way!
I would appreciate other input and the other fuell ratings! I appreciate it! Remeber please- no 8.1 with allison trans comparisons. They aren't offered on the Sub, so they wont help me!
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2004 2500 Suburban LT 4X4 with 8.1 and 3.73 rear.
Prodigy V2.4
BFG All Terrain Tires- AWESOME! New Exhaust to come shortly...
2005 SX230 Yamaha Jet boat!
No camper-yet
(Traded in for above) 2001 Silverado 2500HD 6.0 / 4.1 with BFG Mud tires, dual flowmaster exhaust
Quick question- When you ordered your 8.1, was it just the additional cost of the bigger motor or where there other 'mandatory' packages that you had to include which up'd the cost of the truck?
Quote: I am just curious how you are able to get better gas mislege with a 500CI motor and 3.73 then I am with a 360CI and 4.10? Did they just improve the motors that much?
Exactly why I got the 8.1/3.73 combo over the 6.0/4.10…slightly better gas mileage and lots more power! Probably more to do with the gear ratio than the engine. The city/highway mileage I stated is not towing, while the towing mileage I stated is mostly highway/freeway with only some city driving.
The only required “option” (now there’s an oxy-moron!) with the 8.1 was the Autoride suspension. I think the only options I didn’t get was the sunroof and DVD system (which you can’t get both of at the same time), and the sticker price was around $54k.
If you could only get the Duramax/Allison combo in a Suburban.
My 2000 Burb 6.0 w 3.73 gets 10.5 mpg average towing my 6500# trailer. 16-17 mpg running solo on highway. Under 10 mpg solo in town. The only time I wished I had the 8.1 or 4.10 is in the mountains.
Winnebago Sightseer 35N
was camping with:
Tent '96
Slide-in '98
Coleman pop-up '99
29S Cherokee TT 2000
Me, wife, and two boys 12 and 9
I asked this very same question a few weeks back. I got quite a few answers, and what I came up with based on those answers was the following.
6.0/3.73 - 13 city 16 hwy
6.0/4.10 - didn't get enough responses
8.1/3.73 - 12 city 14 hwy
8.1/4.10 - 11 city 13 hwy
I am guessing that the 6.0/4.10 combination will be real similar to the 8.1/3.73.
I did an awful lot of thinking about this, and I reached the conclusion that the 8.1/4.10 was the way to go, so that is the one I ordered. The difference in final drive ratio is exactly 10%, which means in a given gear at a given speed, the 4.10 will operate at 10% higher RPM than the 3.73, which would equate to a 10% difference in gas mileage (roughly). This assumes zero loading, basically driving the vehicle on a flat road etc. If you start to load the truck, by say driving into a wind or up a hill or something silly like that, then the 3.73 will give back some of its mileage advantage. This is because the 4.10 is operating at about 10% higher horsepower than the 3.73 (the horsepower curve is close to linearly increasing with RPM). This should mean that I will have to step on the accelerator slightly less, and down shift later and for less time in the 4.10 than the 3.73. That would account for why the mileage numbers aren't really 10% different, especially when towing (some people suggested better numbers towing with the 4.10 than with the 3.73).
For me, the 8.1L was a given, I just couldn't get where I wanted to be in towing capacity with the 6.0L That being said I decided I could live with a less than 10% hit in gas mileage in order to improve my towing capabilities.
Now, keep in mind that my opinion is always worth exactly what you pay for it .... nothing.
Quote: I am just curious how you are able to get better gas mislege with a 500CI motor and 3.73 then I am with a 360CI and 4.10? Did they just improve the motors that much?
Exactly why I got the 8.1/3.73 combo over the 6.0/4.10…slightly better gas mileage and lots more power! Probably more to do with the gear ratio than the engine. The city/highway mileage I stated is not towing, while the towing mileage I stated is mostly highway/freeway with only some city driving.
...snip....
Another reason is type of engine. Small block vs big block and the philosophies that go with it.
Small block is high rev'ing engine with decent amounts of torque. Since HP forumla is: HP = torque x rpm / 5252, can see why small blocks have such large HP numbers...they rev' higher and are designed to.
Big block is tough to rev high, even greater potential of blowing it up. My 7.4L red lines at 4.8K rpms and only gets 290 HP. My 2 seater's 3.1L engine (in restoration, so only numbers from cam sheet and engine builder) spec's out at +310 hp. This is half the volume size in engine...but...rev's to +8K rpms. Also why Indy 500 engines will have 800HP-1000HP but puny torque numbers.
Now why the difference or similarity in MPG. Three things.
1) Sips of fuel per rev, per mile. Small block takes lots of rev's to get those high HP numbers, so lots and lots and lots of smaller sips of fuel to do same/similar amounts of work vs a big block. Big block guzzzzls fuel per rev, but not as many rev's being needed to do same amount of work.
2) Gearing. The small block will drop back into lower gear sooner and stay there longer than a big block. This goes back to #1 above.
3) Throttle setting doing same work. Small block usually has higher throttle setting, married with #1 & #2, gets many, many, many more sips per mile and those "sips" are approaching "gulps"...
-Ben Picture of my rig
1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
Sold the boat (looking for another): Trophy with twin 150's...
51 cylinders in household, what's yours?...
I have a 2001 Yukon XL with the 3.73 and 6.0L in the 1/2 ton. I thought that the 8.1L would be too much of a gas hog in the 2500. I also use it as my daily driver and put on about 35,000 miles per year. My daily is from Aurora to Elgin, and then visiting customers all over Chicago area.
Also, I tow a 7,200 lb boat, and even going to the big lake, up to Lake Geneva, or the Illinois River, I can't keep it in OD, as it keeps on down shifting. The powerband on the 6.0L does not match well with the 3.73 for that much weight.
For milage, I average about 13-14 combined, at best. On 355, at 65 (W/ CC on) I have gotten as high as 18 average, but with no stop and go. Had I known this when I bought the 6.0L, I would have bought the 8.1L. Gas milage is not that much different. The 6.0L is a good engine, but you definately pay for the power. If it were me, I would do the 8.1L and 4.10. You won't get the best gas milage, but you will not be much worse off than the 6.0L, and the power ...
Get the 8.1L with either ratio. Your mileage will be so similar it won't matter. When your fightin a head wind or a hill towing with a full load and you don't even know it, that's all that matters.
2-3 more miles to the gallon shouldn't make or break you at the end of the month if your already considering spending over $30k on a truck to pull your toys to enjoy your already expensive enough hobbies. Just don't let some salesman tell you that 2500hd with 6.0L can handle anything. Most salesmen don't even drive big trucks or have even ever towed anything. I upgraded to the big block from my smallblock and don't have any regrets.
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