From the CAIG website:
When do I use DeoxIT® D-Series vs DeoxIT® Gold G-Series vs DeoxIT® Shield S-Series ?
DeoxIT® D-Series.
General purpose cleaner, for all metal surfaces with severe oxidation and corrosion. If there is a discoloration of the metal - it is considered severe. Use DeoxIT® to dissolve contamination, as well as lubricate and protect the surface. For reference, DeoxIT® has approximately 20% cleaning action.
DeoxIT® Gold G-Series.
For plated surfaces (gold and other precious metals). Recommended for critical applications where only slight cleaning action is necessary. For reference, DeoxIT® Gold has approximately 0.5% cleaning action. If the surface looks clean, applying DeoxIT® first is usually not necessary. If small amounts of oxidation are present on the surface, DeoxIT® Gold will dissolve this. Apply DeoxIT® Gold after DeoxIT® on plated metal surfaces, except where noted with DeoxIT® Shield below. The more critical the connection/part, especially low current applications, DeoxIT® Gold should be the final step.
DeoxIT® Shield S-Series.
Suitable for all metal surfaces tp seal and protect. Recommended after DeoxIT® for best protection or on NEW metal surfaces (usually in the manufacturing process). Also ideal where high degrees of pollution (sulfur, salts, acids, etc.) are present. DeoxIT® Shield should be applied to clean surfaces - after applying DeoxIT® or using an ultrasonic cleaner. For reference, DeoxIT® Shield has 0% cleaning action.
DeoxIT® Fader F-Series.
DeoxIT® Fader F-Series is a precision lubricant specifically formulated to improve conductivity and lubricate conductive plastic and carbon compound faders, switches and other similar components.