I am new to Marklin and recently received a number of Marklin locos and rolling stock that have been sitting in a case behind glass for about 27 years untouched except for a dehumidifier that has been running in the room during the summers. Prior to this resting period they were well cared for by a meticulous 27 year Marklin collector. All the pieces are older and were purchased on the secondary market between about 1963 to 1990. I plan to sell on Ebay the pieces I will not be adding to my own collection (unless there is a better way?) but would like to take each loco on a short test run before I sell them to confirm they run and have no issues. I am looking for some advice as to what maintenance I should take with the locomotives to ensure no damage is done during the short test runs on my layout. I just ordered a bottle of LGB Marklin Trix oil with a needle applicator so I hope I am on the right track.

Any advice would be appreciated by this new Marklin fan.

Jeff,
When I brought my old (analog) loks out of storage after 30 plus years, I basically only needed to do a light (operative word: light!) oiling per the instruction manuals. I needed to replace a few springs on some reversing units, and one lok needed new traction tires. Apart from that, they were good to go. I then bought a few (again, analog) locomotives off eBay, and some needed the gunk that was stuck in the gears and wheels cleaned out - after that and the oiling, they run just fine. The older loks are very hardy beasts.

There's a very useful Märklin service manual for the analog engines - item number 0733. i just did a search on the site but none of the links appear to be working any longer (or at least for me.) Someone here may have an electronic copy - otherwise, I can make a pdf for you of the hard copy I previously printed out.
HTH,
Fred