Anyone have a GM 8.1?

Hockeygoon · Oct 14, 2020

I have a 2002 1500 Tahoe with the 5.3 and I average about 14 to 16 MPG with every tank of fuel. A local dealer is offering a 2004 Yukon XL 2500 with an 8.1 engine - just how bad is the mileage in something like that? They both have about 150K miles and he's willing to trade for $2k difference.

Both vehicles are spotless with leather, 4X4, no rust, no dents, no fade or tears in the interior.

buickanddeere · Oct 14, 2020

Look for a direct injected 5.3 from 2013 or later .

J Hamilton · Oct 14, 2020

A friend of mine has a 2500hd pickup with the 8.1 and he gets 6-8 mpg, mine has the 6.0 and I get 10-12 mpg

iajake18 · Oct 15, 2020

I have a 2500HD Chevy with the 8.1. Local driving I get 8 to 10 mpg. My in laws live 3 1/2 hrs away, I've gotten 14 driving there. Also, the 8.1's are known to use a little oil between changes.

matthies · Oct 15, 2020

Like Hamilton said 6 to 8, loaded or not, not a daily driver, just a puller and does it pull!!

Switchflicker · Oct 15, 2020

(quoted from post at 06:58:37 10/15/20) Like Hamilton said 6 to 8, loaded or not, not a daily driver, just a puller and does it pull!!

Same in my 32 foot motorhome. 6 to 8 mpg. 1 qt of oil between oil changes. Bullet proof engine. One incident of limp mode, but that was two years ago and it never came back with no intervention from me.
Stan

BarnyardEngineering · Oct 15, 2020

12 running around empty and a LIGHT foot. 10 with the camper in the bed. 8 with the camper and towing a 14' enclosed trailer.

Ken in MN · Oct 15, 2020

I had an '03 2500HD with the 8.1 & Allison transmission. Local driving almost always was 9-10 mpg. Highway was around 12-13 with a best of 14.9 mpg on a long trip. I did get better mileage towing than my brother did with his 6.0, but it wasn't enough to brag about. I drove that truck 11 years. It always used 1 1/2 qts oil between changes.

miangus · Oct 15, 2020

2004 HD 2500 4 wheel drive with the 8.1 and the Allison. It has 4:11 gears so it pulls pretty good. The best it gets is about 10 mpg, but averages about 9 mpg. It does use a little oil between changes, but nothing to worry about.

tomNE · Oct 15, 2020

as said; 8.1 is a great engine if you have use for it. too me, it's way better then a diesel for the average dude! It doesn't fit in as a coffee shop commuter!

rustyfarmall · Oct 15, 2020

I own a 2001 K3500, one ton dually. 8.1, 6 speed manual, and 4.11 axle ratio. Averages 10 mpg. It isn't so much the size of the engine that controls miles per gallon, as it is the axle ratio and configuration of the vehicle.

Determined · Oct 15, 2020

(quoted from post at 21:39:08 10/14/20) I have a 2002 1500 Tahoe with the 5.3 and I average about 14 to 16 MPG with every tank of fuel. A local dealer is offering a 2004 Yukon XL 2500 with an 8.1 engine - just how bad is the mileage in something like that? They both have about 150K miles and he's willing to trade for $2k difference.

Both vehicles are spotless with leather, 4X4, no rust, no dents, no fade or tears in the interior.

Fun to drive torque monsters and who doesn't like to say 496 cubic inch.

I have one in a 2006 Silverado 3500 and one of our sons has one in a Silverado 2500HD both with Allison transmissions.

You will not get the kind of mileage you are seeing from your 5.3 but if you plan on towing with it you will be extremely happy.

I can haul a 15000 lb trailer through the hills and not even feel it behind me.

What mileage you will actually get will depend on diff gear ratio and transmission.

With my Allison 6 speed in 6th gear(overdrive) it is a .6:1 ratio which really helps keep the RPM's and fuel consumption down.

I believe the Yukon comes with the 4L85 transmission which will only give you a .75:1 ratio, the diff ratio of course will need to be factored in.

My son's truck has the 5 speed in it, in 5th gear it is a ,7:1 ratio.

The couple of hundred RPM difference cruising on the highway results in a difference of 1.5 - 2 MPG less from his truck to mine.

GordoSD · Oct 15, 2020

Your Tahoe will wholesale out at about 2500. Why would a DEALER give you a XL worth about the same, PLUS 2k cash? He's telling you your Tahoe is worth 6K retail. Keep the Tahoe. Mine is a 99 5.7, 4:10 axle, 205,000 a
and has never bee opened.Avg 14mpg to town and back.

buickanddeere · Oct 15, 2020

What is a 8.L fuel hog going to do that a fuel sipping 5.3 cant
?

Determined · Oct 15, 2020

(quoted from post at 10:50:16 10/15/20)
What is a 8.L fuel hog going to do that a fuel sipping 5.3 cant
?

Well to start with the 5.3 in your chart makes 376 HP at 5600 RPM.

My stock 8.1 is making over 300 HP at 2000 RPM.
The 5.3 at 2000 RPM is making 130 HP

Torque the 5.3 is making 383 lb ft at 4100 RPM
At 2000 RPM it is listed as 325 lb ft.
My 8.1 is making over 400 lb ft at 2000 RPM
If I need to drop a gear I am making 440 lb ft at a still useable 3200 RPM.

No idea who drives with the engine screaming at 4000-5600 RPM.

The 8.1 makes useable HP and torque in the RPM range it will be driven.

If you tried to achieve the theoretical numbers given for the 5.3 and actually drove at those RPM's I can guarantee you will be using more fuel than my 8.1 for the short life of the engine if constantly run at that speed.

If all you ever haul is groceries then by all means go with the 5.3 but if you tow a lot of heavy loads the 8.1 is legendary.

Brendon-KS · Oct 15, 2020

"My stock 8.1 is making over 300 HP at 2000 RPM"
~No it isn't - that would take 788 lb-ft of torque to achieve.

"My 8.1 is making over 400 lb ft at 2000 RPM"
~That's realistic - with 430 lb-ft you're making 164 hp at that engine speed.

Determined · Oct 15, 2020

(quoted from post at 15:46:03 10/15/20) "My stock 8.1 is making over 300 HP at 2000 RPM"
~No it isn't - that would take 788 lb-ft of torque to achieve.

"My 8.1 is making over 400 lb ft at 2000 RPM"
~That's realistic - with 430 lb-ft you're making 164 hp at that engine speed.

Well Brendon-KS I stand corrected I miss read the graph.

I should have said 170 HP at 2000 RPM according to the graph.

Still considerably more than the 5.3 at that RPM.

Hockeygoon · Oct 15, 2020

I was surprised that the 6.0 actually had more power than the 8.1 and not a whole lot less torque.

Determined · Oct 16, 2020

(quoted from post at 22:23:51 10/15/20) I was surprised that the 6.0 actually had more power than the 8.1 and not a whole lot less torque.

Do an image search for 6.0l torque curve and it will bring up graph's that will show you where the power of the engine is being made.

Much like the 5.3 the 6.0 is screaming to make it's power.
Power and useable power are not the same thing.

Other son has a 6.0 in a 2005 GMC 3500 and no it is not a slouch.
Empty he gets better mileage than I do.

We have both hauled the exact same trailer and load before and he burns more fuel than I do with my 8.1

buickanddeere · Oct 16, 2020

(quoted from post at 11:50:16 10/15/20)
What is a 8.L fuel hog going to do that a fuel sipping 5.3 cant
?

You are not driving at full output all the time . The engine is not always operating at 5600rpm .
The engine is not going to wear out or blowup being revved up on hills .
You time trailering is only 5-10% of the duty cycle of the truck .
I have no idea why some people think their light duty application is HD . If you what to worry about rpms and engine life . look at marine propulsion , 24/7 power generation , irrigation etc that runs for years at a time .

Carls70 · Oct 16, 2020

A 1/2 ton 5.3L VS a 3/4 ton 8.1L is kind of an apples to oranges comparison IMHO. In my experience the 8.1L is a stout simple engine that can pull all day without knowing anything is behind it. As others have said, expect more fuel consumption than a 5.3L or 6.0L when running EMPTY, expect a much quieter pleasant towing experience with an 8.1L at the same or better mileage than a similar vintage 5.3/6.0L when LOADED/TOWING.

My experience is with 3/4 ton HD trucks and I prefer the 8.1L in general to the smaller engines.

Carl

buickanddeere · Oct 17, 2020

Depends what vintage of engine . The 2014 and later direct injection engines have more power and improved efficiency vs the earlier port injected engines .
The 6.2L with the Max Towing option that the wifes truck has . It will walk all over a 8.1 loaded or empty .

Carls70 · Oct 17, 2020

Agreed. Overall I personally prefer a slower turning larger displacement engine to a smaller faster turning one. That said the new D.I. cam phaser engines are a new world of HP/Torque curve compared to the iron TBI/PFI engines. Though I am interested to see how the fuel delivery systems age as I have seen several with failed injectors. I also wonder about the overall valve train life of the current ones (hopefully better than the early AFM engines)

Carl

Anyone have a GM 8.1?

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