I come from driving schwan's trucks where the topkicks all had liquid propane injected 8.1's. Combined with the 4.56/4.88 gears the propane would give us a run at the diesel guys. They were a LOT spunkier than your garden variety 8.1.

 

Well I did not end up buying the 06 with the 8.1 instead I went for this low milage 2000 GMC 3500 I wanted a snowplow truck and the rclb dually with the bigblock just was a bit overkill for the intended use. Next time maybe

 

although mine isnt nearly moded like you two guys is, but I will back the 8.1L! i got some good feedback from guys who tow huge 33'+ campers/boats around the country, and some of these guys had 300-400k on the motors!! Very dependable if you service it regularly. mine has just over 97k and the only thing mechanically i have put into it was a crank sensor....

 

1 quart every 900-1000 miles....

 

holy crap, these big blocks use all the oil they possibly can, both in gas and engine oil.

 

my dad has loved his 496 since he got his suburban back in 01. It's about to top 170k miles and he claims it gets 16mpg on the highway whether or not he's towing his boat. His is RWD with 3.73s with the 4L80E. I don't know the tire size though. He's been using a K&N filter for several years and claims it did help mileage and power. It will still chirp the tires in wet weather. He said it only uses a quart every 5k miles.

He's got a friend with an 02 BB Suburban that is getting ready to sell it. He is planning on buying it from him when he's ready to sell.