Unloaded Performance

ebod · March 10, 2003

How much difference is there in the performance in the 6.0L and the 8.1L engines when you are hauling little or no weight?

Of course, I'd appreciate info on 0-60mph times, 5-60 mph times, 1/4 mile times, etc. I'd also appreciate a seat-of-the pants assessment from those who have driven both.

Also, how big is the MPG difference between the 6.0 and the 8.1 unloaded?

For what it's worth, I'm deciding between the two engines as well as between a Suburban and a pick-up (2500HD crew cab). Either one will be a 4x4 and have the 4.10 axel ratio.

Thanks!

Gunruner · March 11, 2003

OK here's my spin. I like Suburbans and the Avalanch but I just couldn't give up the truck. I know for sure if I bought a large SUV I'd need to move alot of stuff right away and wouldn't be able to. I wanted a Diesel but alas no dealer would discount any diesel and I got the deal of the century on my '03 K2500HD Ext-Cab with 6.0L and 4.10 locker. I didn't consider the 8.1 as I know the big blocks and fuel use. If I could have justified the need for power I'd go for the 8.1, but the 6.0L is all I'll need. Largest load will be 8,000lb travel trailer and gear. The 8.1 will beat the 6.0 in acceleration and pulling power in the same truck, that's a fact! However, my 6.0 will really pick-em-up and put-em-down. It isn't snap your neck hot rod HP it's power torque and your at 90 in a blink. I just hit 3,000 miles and already gas mileage is in the high 13 mpg average. I got an honest 14.5 on a mostly interstate run. I do think 15 will be easy on a total interstate run. Since my truck is daily driver and mostly unladen the 6.0 was the logical(prudent) choice. I have a friend with the 8.1 and he claims never to have hit the 13mpg. His best was 12.5 approx, that is what he told me. I was getting that during the stay below 55mph 500 mile breakin. My truck does the best mpg between 65-70 mph so far. I never got below 12.4 mpg at any time, even around town. I'm very happy with the 6.0 and have no regrets(so far). Hope this helps.

bigkite · March 11, 2003

It comes down to

Need

Want

Cost

If you need power to haul/tow/ etc. get the 8.1

If you want the biggest gas engine, big hp, big torque, get the 8.1

If cost (initial and operational) is a concern, get the 6.0

People have been happy with both engines so there is really no wrong choice. It all depends on what is important to you.

CMNTMXR81 · March 11, 2003

Believe it or not, unloaded I'd say the 6.0 would be door to door with the 8.1 in a 0-60 run. But that's not because the 6.0 is soooo powerful and the 8.1 is weak.

It has to do with the fact that the 8.1 is laden with the Allison transmission which as I've repeated before ISN'T programmed for stop light drag racing. In unloaded contests like this it IS a burden. It shifts about 500 - 750rpm short in each gear and depending on throttle position can sometimes completely not use either second or third gear by quickly shifting past it and into 3 or 4.

However, slap a 16,000lb trailer out behind both and repeat the same 0-60 contest and the 8.1 & Allison show it's merits. Mass requires torque to move it from a dead stop...the 8.1 and D-Max's make more torque at idle than many engines on the market make at full tilt.

ebod · March 11, 2003

The programming issue is an interesting one that I haven't considered.

Just out of curiosity, (i) would putting the tranny in the tow/haul mode minimize the transmission programming glitch (I don't even know for sure that the 8.1's tranny has the tow/haul mode); (ii) do any "chips" or engine software reprogramming products eliminate the problem; and (iii) why is the truck programmed in the way you describe?

My real world craving for acceleration isn't tied to stoplight drag racing (although sometimes I need to be able to accelerate quickly from a stop). Does the programming issue make as much of a difference in street/rolling starts and/or in highway passing acceleration?

Thanks again.

CMNTMXR81 · March 11, 2003

Of course the Allison has the tow/haul mode. But that won't make much difference in an unloaded truck.

It's programming in general is designed for towing/hauling not for pure acceleration. As such, no matter how you look at it, the trans is shifting for work patterns rather than performance patterns.

Not to say that the 8.1 is a slug or anything, it's far from actually. I take people by surprise with it all the time, but I wish it had another 500-750rpm in each gear and wouldn't short shift through second or third like it has a tendency to do.