Every unit that is properly tuneup will burn any type of fuel cleaner, saving you money and reduce pollution.
It's quite likely that your outside AC unit is surrounded by plants, shrubs, trees, or fencing.
These can block your unit's air flow, so you want to make sure that there is at least one foot of free space between your unit and any other objects.
The same holds true for an indoor unit. You want to keep it unobstructed, so avoid having curtains or drapes hanging over a unit while it is in operation.