http://www.busnut.com
is the site to ask these questions. I've got some manuals in PDF format somewhere. If the bus is running good, and you drive it right it can get 10+ mpg; I've heard reports of near 14 mpg. The bus is all aluminum, so it's pretty light for it's size. PD4104's have an air actuated shut-off called a skinner valve, unlike our skoolies which have (usually) an electric shut-off solenoid. It's a common failure point, and difficult to diagnose if you're new to the bus. It'll suddenly shut down, as though it has a fuel blockage (clogged line or filter). It may or may not start back up, when it feels like it. The skinner valve is located on the firewall behind the engine; check the electric connections before you drive it any distance!!!!! Has an air line going to the fuel linkage. Don't ask how I know all this....
No, I no longer have one. There's a HUGE amount of support out on the web; just don't go lookin' on the school bus sites!!
Good luck!
Email me and I'll look for the manuals
winnemuccadave@NOSPAMnetscape.net
remove the obvious