well my manual, on re-reading, indicates not to use it on wet track-cos all you do is spread wet black stuff around-whcih i know from looking at my LGB block when i have used it on wet areas-just a black, wet mess that travels along the rails
but my manual, for the early decoder version, specifically mentions the EMF feature and that the loco will run constant on curves and grades -which implicitly seems to mean, to me, use on grades is acceptable-and it is designed for this purpose. There is no specific mention of not using it on a grade at all.
HOwever, as i have stated before, and as i recommend, i did reverse the grinding wheels because, on grade, particularly with sap, my engine used to mambo--a sometimes perfect equilibrium between traction of the loco and reverse push traction of the rough grinding discs on grade-up and back and repeat!
Once reversed this was eliminated , and imho, much for the better.