Ford 2007 F-650 Owner's Manual page 31

Instrument Cluster
Hourmeter (if equipped):
Registers the hours the engine has
been operating.
Air filter restriction gauge:
Measures the vacuum inside the air
cleaner. The more the air cleaner is
restricted (dirty, clogged), the
higher the vacuum reading. Change
the air filter when the gauge reads
25 inches. After installation of the
new filter element, reset the gauge
to 0.
30
2007 F-650/750 (f67)
Supplement
USA (fus)