Join Date: Jun 2016
Location: Orange County, CA
Chassis: Crown Supercoach II (rear engine)
Engine: Detroit 6V92TAC, DDEC 2, Jake brake, Allison HT740
Rated Cap: 37,400 lbs GVWR
A) Don't lug it.
B) Don't overheat it.
C) Use only CF2-rated straight 40-weight oil in it.
Do that, and it could outlast you. Don't do that, and it will go bad on you in a hurry. Detroits are good engines, but they need to be driven correctly.
Incidentally, it's MCI - Motor Coach Industries. What is it, an MC9, or something older? Who owned it last? (If it's a church, be careful, very very careful.) You need to do your research first, and inspect it thoroughly.