6.0 vs. 8.1liter engine

carload4916 · March 3, 2013

I am looking at buying a used Chevy 2500hd and debating on which engine to get. This truck will get used on a farm as a work truck so it will do some towing from time to time but also as a run around vehicle. I wouldn't say really heavy towing. I would say the heaviest towing it would do is hauling a livestock trailer load of 4 cows. But again, that will not be everyday. It will get driven empty more than loaded. It will also be hauling firewood as well.

I heard many places the 8.1 is worse on gas mileage. To me, I am not to worried about gas mileage since I don't have to drive it to work everyday. And since I am currently driving an s-10 zr2 model, I am used to bad gas mileage. I have also heard that the 8.1 uses a little oil. How much does it use? Is it bad enough to have to add oil in between changes?

The only reason I am considering the 8.1 is because of the Allison transmission. I just don't know if the 8.1 would be way to much truck for me. Is there no chance of getting the Allison with the 6.0?

What about the axle ratio? How much of a difference does that make? Which one is the more desireable ratio, 4.10 or 3.73?

I am not going to get a diesel just for the fact that it will not get driven everyday and when it is driven, it will be short trips. That is just to hard on diesels.

Sorry if this has already been discussed before.

Edited March 3, 2013 by memory1

ATMINF · March 3, 2013

The 8.1 motor is very strong, uses about a quart of oil every 2000-3000 miles. The gas mileage is around 8-11, but when towing, it will not drop too much. The 6.0 uses about a quart every 4-5000 miles, mileage ranges from 12-15, but when towing it will drop to 6-10. The Ally transmission only came with the 8.1 or D-Max. The 6.0 came with the 4l80, and the new ones come with the 6L90( it's a 6 speed, and some think its a Ally, but it is not). The 8.1 also came with a beefed up 4L80 called a 4L85. Good luck.

music · March 3, 2013

Your only choice post ~2007.5 is the 6.0 w/ the 6L90e transmission. It tows well, and gets better mpg than an 8.1. Pre-2007, I'd probably go 8.1L if I could find one that I liked, but would look at the rest of the truck much more-so than the motor.

carload4916 · March 3, 2013

The 8.1 motor is very strong, uses about a quart of oil every 2000-3000 miles. The gas mileage is around 8-11, but when towing, it will not drop too much. The 6.0 uses about a quart every 4-5000 miles, mileage ranges from 12-15, but when towing it will drop to 6-10. The Ally transmission only came with the 8.1 or D-Max. The 6.0 came with the 4l80, and the new ones come with the 6L90( it's a 6 speed, and some think its a Ally, but it is not). The 8.1 also came with a beefed up 4L80 called a 4L85. Good luck.

What is the deal with these engines using motor oil? Is it all the Vortec engines or just these two?

Your only choice post ~2007.5 is the 6.0 w/ the 6L90e transmission. It tows well, and gets better mpg than an 8.1. Pre-2007, I'd probably go 8.1L if I could find one that I liked, but would look at the rest of the truck much more-so than the motor.

Why would you go 8.1 if earlier than 2007? I am looking at a truck in the range of 2000 to 2007. I do not want the new style, just don't like the looks of them and plus I wouldn't be able to afford it.

I guess I am trying to decide if the Ally transmission is worth it. From the little bit or research I have done, the 8.1 would have way to much power for my situation. I do plan on keeping this truck for a while. I am just worried that if I buy the 8.1, 3 or 4 years down the road, I will regret it because of the gas mileage.

If buying a new truck, can you get the Ally trans with the 6.0 if you custom ordered a truck? I am not going to buy new, just curious why they don't offer the Ally trans with the 6.0.

Edited March 3, 2013 by memory1

music · March 3, 2013

New trucks have the 6L90e 6-spd. It's a strong unit, and GM's replacement for the Allison w/ gas motors. My only reason for 8.1L prior to '07 is for the torque. I tow a camper, and the 6.0 vs 8.1 mpg isn't much different in the older models (from what I've read/seen). If you'll be doing a lot of hwy miles, the 6.0 will do a little better. Not much difference around town, since both are *bad*.

kstruckcountry · March 3, 2013

It depends on the truck as to how much oil it burns, but they do seem to burn more than the half tons by far. Find a nice clean truck in good shape, and I think you'll be happy. I wouldn't really worry about which engine, although the 8.1/Ally is nice. You'll pay plenty for fuel in either.

If you even feel bad about how much you're spending on fuel, find a guy with a late 90's Ford with a 460ci and ask him his MPG.

doverarjim · March 3, 2013

As a past 6.0 owner who pulled more than what you are looking at, and has owned a LOT of bb Chev's over the years. I would say that you will be fine with the 6.0, also you will be hard pressed to find a 8.1 that has not been overworked and cost more in the long run in repairs.

As far as oil use in the bb it is the nature of the beast, you run one it will use a little oil just the way it is, since 1964.

GM does not offer the Ally with ANY engine other than the Dmax no way to get one, and I have not seen an adapter that would allow one to be put behind any other engine.

ATMINF · March 3, 2013

The 8.1 motor dates back to the late 60's tech. Also chevy big blocks have always used a little oil, it's part of how they run. I would say its part of the norm for them, but the LS series motors are 90's tech and they incorporate all the new knowledge that comes with that. So the bottom line is that all engines will use oil, some more than others. Hope that clears things up. As for the Ally trans, it only comes with the D-Max, no way to get it otherwise.

kstruckcountry · March 3, 2013

You got an Ally with the 8.1. But I agree that OP would be fine with a 6.0.

Edited March 3, 2013 by kstruckcountry

8.1HD/ALLISON · March 3, 2013

I would take the 8.1 anyday over a 6.0. Have had the pleasure of driving them both. Loaded & unloaded. If you can find a good 8.1 take it. Fuel mileage difference is minimal. Not saying the 6.0 won't work for ya, but having too much is better than too little.

carload4916 · March 3, 2013

The 8.1 motor dates back to the late 60's tech. Also chevy big blocks have always used a little oil, it's part of how they run. I would say its part of the norm for them, but the LS series motors are 90's tech and they incorporate all the new knowledge that comes with that. So the bottom line is that all engines will use oil, some more than others. Hope that clears things up. As for the Ally trans, it only comes with the D-Max, no way to get it otherwise.

The 8.1 motor dates back to the late 60's tech. Also chevy big blocks have always used a little oil, it's part of how they run. I would say its part of the norm for them, but the LS series motors are 90's tech and they incorporate all the new knowledge that comes with that. So the bottom line is that all engines will use oil, some more than others. Hope that clears things up. As for the Ally trans, it only comes with the D-Max, no way to get it otherwise.

The 8.1 motor dates back to the late 60's tech. Also chevy big blocks have always used a little oil, it's part of how they run. I would say its part of the norm for them, but the LS series motors are 90's tech and they incorporate all the new knowledge that comes with that. So the bottom line is that all engines will use oil, some more than others. Hope that clears things up. As for the Ally trans, it only comes with the D-Max, no way to get it otherwise.

You can get the Ally trans with the 8.1.

I would take the 8.1 anyday over a 6.0. Have had the pleasure of driving them both. Loaded & unloaded. If you can find a good 8.1 take it. Fuel mileage difference is minimal. Not saying the 6.0 won't work for ya, but having too much is better than too little.

I was kind of thinking along the same lines. I would rather have it and not need it then need it and not have it. This is just one of those things that I need to decide on myself.

8.1HD/Allison, the truck I am looking at with the 8.1 looks identical to yours, even the color. What does CCLB stand for?

kstruckcountry · March 3, 2013

Crew cab, long bed

ATMINF · March 3, 2013

I would say a 8.1/Ally truck is more capable than a 6.0L in all aspects, but that does not mean a 6.0L truck is not capable. I like my truck a lot, and it has been able to do everything I need it to do. If I were to do it all over again I would have bought a white 8.1/Ally 4x4 crew cab long bed, that was sitting next to my truck,but it was also $12-14 grand more than my truck.

sillywillie07 · March 3, 2013

I read somewhere that if you put a lower temp thermostat in the 8.1 it will use less oil. There is a link to a web site that has lots of info on the 8.1l. Also upgrade the spark plugs and gap them, will help with power and mpg.