6000 vs 8100 mileage

rob77 · July 13, 2004

I am buying a 3500 Chassis Cab, which will be fitted with a flat bed / stake body. The truck will be driven mostly long highway trips, at near maximum payload, no trailer. Trying to decide between 6000 and 8100 engines. No diesel please. A salesman told me the 8100 with 4.10 rear will get 3 mpg more than the 6000. Should I believe him? Do I need the extra power if I am not towing a trailer?

Shaners · July 13, 2004

It's possible that when fully loaded, the 8.1L would get better MPG's, but not 3 MPG's in my opinion.

I have the 6.0L in my truck and tow an 8500 lb camper. My buddy has the 8.1L in his Avalanche and tows a 6500 lb camper. I get about 1/2 -3/4 MPG less than he does, but I'm also pulling a bigger load. However, he can run away from me if he wants too... Also he is just lugging along in OD where as I'm truning some revs in "3".

Empty is another story though, where I can consistantly get 3-4 MPG's better than him.

With the milage numbers being so close when loaded, I would suggest the 8.1L if nothing else, just for the extra power when needed especially since you will be loaded heavy.

"There's no replacement for displacement".

snoman · July 13, 2004

I am buying a 3500 Chassis Cab, which will be fitted with a flat bed / stake body. The truck will be driven mostly long highway trips, at near maximum payload, no trailer. Trying to decide between 6000 and 8100 engines. No diesel please. A salesman told me the 8100 with 4.10 rear will get 3 mpg more than the 6000. Should I believe him? Do I need the extra power if I am not towing a trailer?

I would question that. With a very heavy load and in hilly terrain, the 8.1 might do better. But around town not towing it would do worse. The 6.0 is a strong engine for its size but need to turn about 500 to 1000 rpm faster than 8.1 to make its best power. If towing is your game and you plan to tow a lot, go for the 8.1 unless you want a 6.0 and you are unhappy with it you can regear it. (I do not like that Allison tranny that you have to get with a 8.1 if you want a automatic though) If the 6.0 had 4.56 gears vs a 8.1 with 4.10's the differece would not be as great because the 6.0 would be able to wind up a little more at any given speed to make its best power because even though the HP ratings are simular, the 6.0 will never have the torque of a 8.1 so you have to make it up with gearing.

XTOAK · July 13, 2004

Another item to consider besides mileage and torque is the transmission. The Allison is hard to beat and IMHO is alot better than anything you'll find mated to the 6.0L....yes, I have the 6.0 and find the tranny adequate but "it ain't no Allison". I shopped for mileage too and should have considered the Allison a little more into the equation as I would have bought the 8.1 hands down.

snoman · July 13, 2004

Another item to consider besides mileage and torque is the transmission. The Allison is hard to beat and IMHO is alot better than anything you'll find mated to the 6.0L....yes, I have the 6.0 and find the tranny adequate but "it ain't no Allison". I shopped for mileage too and should have considered the Allison a little more into the equation as I would have bought the 8.1 hands down.

Hey now, the 4L80's roots go back the the THM400, one of the thuffest trannies ever made. I have seen them behind 700+ HP drag cars and go several seasons without a rebuild. THere it NOTHING wrong with a 4L80 behind a 6.0 and it will last as long or longer than a Allision will behind a 8.1 becuase that Allision has had problems since day one and still is. The main reason that GM came out with the Allison is two fold. One is that the Duramax has such a narrow RPM range were it pulls good (around 1000RPM) that 4 gears would not keep it there towing and the second thing is PROFIT. They make more money on each ally than they do on each 4L80.

willscary · July 14, 2004

I also think the 4L-80E is a great tranny. I may be mistaken, but I think the 8100 can be mated to the 4L-85E.

snoman · July 14, 2004

I reread orignal post and I see that there will be no trailer used. Get the 6.0 with 4.10 gears.

Roofer · July 14, 2004

Just my opinion, but always go bigger. You will always regret not getting more power. Being close or over payload most of the time, you will want the torque of the 8.1. The Alisson cannot be beat when hauling or towing heavy loads.

westca707 · July 14, 2004

To get the fuel mileage of the 6.0, I would get the 8.1/Allison with the 3:73 rear end instead of the 4:10's.

snoman · July 14, 2004

Just my opinion, but always go bigger. You will always regret not getting more power. Being close or over payload most of the time, you will want the torque of the 8.1. The Alisson cannot be beat when hauling or towing heavy loads.

He said he will not have a trailer though ever and the 6.0 will haul anything that can be loaded on the chassis and cost about 3000 less too without the 8.1 anf the Allision.

linda · July 14, 2004

The Allison is a superb trany, feels very tight in every gear. For any long distance driving, towing, or whatever....the Allison is fantastic. I have NEVER had one ounce of trouble from it. Who knows what will happen tomorrow, next week, or next month. Maybe you will have to tow something that you didnt expect to. Its always better to have the ability to do what you need, even if you never have to. By all means, without exception, get the 8100 with the alli and 4.10 rear. I can only imagine you have not test drove one of these yet in comparison to the 6.0, because your mind would have most definately been made up by now. Go down to the dealer and test drive each one........then see how you feel.

Good luck.

Roofer · July 14, 2004

Just my opinion, but always go bigger. You will always regret not getting more power. Being close or over payload most of the time, you will want the torque of the 8.1. The Alisson cannot be beat when hauling or towing heavy loads.

He said he will not have a trailer though ever and the 6.0 will haul anything that can be loaded on the chassis and cost about 3000 less too without the 8.1 anf the Allision.

Ya I saw that. Never say never. Just like linda said, you don't know when you'll all of a sudden want to tow something. Besides, hauling close to max payload is more stress for power than towing. Our F550 is only used for hauling. It is at or above max GVW every day. The one part I wish we would have added since day one was a trailer hitch. I am glad though that I got the diesel instead of the V10. It still needs more HP.

snoman · July 14, 2004

I have to disagree here because a extra 4000 lbs on truck does not add as much extra load and drag as a 4000lb trailer with its wind drag and added power loss from the tires and axles on it too. I remember when stake bed truck came with 6 bangers and they survived for years in some really nasty jobs and loads too and today a 300HP 6.0 is not enough?. My neighbor bought a very clean 65 1 ton stake bed a few years ago that is stock and has a 250 6 and a 4 speed in it and he hauls all kinds of stuff with it without any problem. I saw a guy in a parking lot the other day at a car parts store working on a 78 1 ton stake bed that had a bad vacum hose. Truck had close to 200k on its 350 and 4 speed and was stock and he was hauling A/C units that go on large builds roofs and that weight a few tons each. He had on on truck and a few on a trailer behind it and said it got along fine still. If original poster can live with a stick, he might try a 6.0 with one and a 4.10 as it would be a real stump puller and it will haul or tow anything he wants to and get the best possible MPG of all the combos listed and be the cheapest yet to buy too.

Charlie in TX · July 14, 2004

THere it NOTHING wrong with a 4L80 behind a 6.0 and it will last as long or longer than a Allision will behind a 8.1 becuase that Allision has had problems since day one and still is.

Do you have any idea what your talking about? There is no way the 4-80 is better or stronger than an Allison. 'it will last as long or longer than a Allision' please.

Proove the Allison 'had problems since day one and still is'. How many Allison 1000s have you had? How many of them failed? How many failure has the Allison 1000 had? How many failures has the Allison had vs the 4-80 under the same load?

Whenever you call someones equipment junk you need to back it up.

XTOAK · July 14, 2004

I have to agree with Charlie in TX on this one as I was a little surprised with the comeback from Snoman. Granted, the roots of the 4L80 may go back to some stout beginnings but I'd hate to put one up against an Allison. I've driven/owned a couple trucks with Allisons, and they took a beating yet kept on pulling. I wouldn't even consider putting my 80 through the same torture that the Allisons went through as it would suffer a very premature death.

But, to understand your conclusions, why do you say the Allison is bad? What problems is it having? Thanks.