Necessity of using a conductive contact lubricant at selected loco and tender locations

It's never a bad idea, but it's not mandatory either.

I have three of the AM Pacific engines. One was converted to TMCC which I run frequently on the layout. AM engines would be considered modern rather than postwar. They are built much different than the Gilbert engines. I have both the Bachmann conductive lube which is a very thin liquid, and the MG Chemicals Silver Conductive Grease. I have never used them on AM engines, no reason to. If you do decide to use them be very careful where you put it and how much is used. The American Models insulators between the wheel and axle are very thin and it would be easy for the conductive thin oil to bridge that gap.

The DCC signal information, unlike Legacy, is transmitted over the rails. If you experience DCC dropouts you could try it.

Where I use the conductive lubes is on the newer Lionel Legacy diesels at the journal boxes. These are poorly designed and out of the box most do not run well. After the factory conductor springs under the journal boxes are replaced with heavier gauge springs I use the lube to assure conductivity.

On my Flyer stuff I use the same light oil on the tender axles/wipers that I use to lubricate everything else. Not sure that it is that important to use a special oil.

Thanks, guys!

Someone correct me if I am wrong: but I think that the only truly conductive lubricant might be graphite?  Aren't the "conductive" oils and greases able to claim that due to a very thin film rather than the product itself being conductive?? 

There are carbon based conductive lubricants available and they are usually inexpensive. The better ones are either copper or silver based and are truly conductors. The silver based grease is also very expensive, the Bachman EZ Lube is quite a bit less.