Obviously his selling dealer didn't explain the "benefits" of AFM or he didn't get an owner's manual.
Active Fuel Management®
Vehicles with V8 engines may have
Active Fuel Management. This
system allows the engine to operate
on either all or half of its cylinders,
depending on the driving conditions.
When less power is required, such
as cruising at a constant vehicle
speed, the system will operate in
the half cylinder mode, allowing the
vehicle to achieve better fuel
economy. When greater power
demands are required, such as
accelerating from a stop, passing,
or merging onto a freeway, the
system will maintain full-cylinder
operation.
If the vehicle has an Active Fuel
Management indicator, see Driver
Information Center (DIC) 0 152 for
more information on using this
display