Exposed gears on trucks

Rule of thumb: Grease is for Gears.

A little goes along way. If you are picking up excess debris from the track, your track is too messy and you have too much lubricant.

I use Labelle 102, 107, 108 and 106 along with Red N Tacky #2.

So you are using the r and t on those gears ? 

A little Red And Tacky on exposed gears has always worked for me. No problems.  Unless you are on carpet or in a windstorm, how are you going to pick up debris?  I suppose you could in a derailment.

A very little grease on the gears, but don't forget a drop of Labelle 107 where the hubs of the idler gears meet the protruding studs.  I've seen excess wear and slop in the idler gears a lot more often than worn teeth.  Yes, broken teeth due to ballast, screws, etc., is a problem, especially with Magnetraction.

I know the consensus is that "twin-vert" F3's like the 2363 are better runners.  But from a design standpoint, Lionel had it right the first time with the Growlers.  No exposed gears.  They didn't sling grease onto the rails, and less risk of fouling from carpet fibers, "snow" or whatever.

Toy Trains are like any other mechanical item with moving parts. Oil and grease for longevity. I remember reading an article on restoring postwar locomotives and after cleaning everything up and cleaning the mechanism with a good dous of minerial spirits, the author mentioned that running the locomotive without out lubrication gives a whole new meaning to "squeeky clean".  Oil and lube and you will have years of satisfaction from your toy trains. I have many post war and prewar locos that are still running fast and furious.