92000 on ours, and yes it burns an excessive amount of oil, but it leaks out of the main seal and oil cooler lines and the tranny doesnt leak but it does slip in 2nd gear. Now, maybe you got a better truck? As ours has gone through 2 fuel pumps, nothing electrical works right, And its spent majority of it time with the check engine light on and not being able to pass IM. This goes along with the other experiences weve had with GM trucks, all the same problems, and they all started around 80000miles. I know ALL trucks have their leaks and especially oil cooler lines, but it started soo early and is so bad that its jsut turned me off of the motor. I would like to stick one in a car and make a monster, but ill stick with my diesel for towing.
One last opinion, i think the majority of the 8.1s somewhat decent highway mileage is due too the allison, it runs at a very low rpm at higher speeds.
PS the guy in your avatar is hilarious