TR3 has proven to be able to clean layers and layers of grime off machines, and I haven't had it damage decals. On a truly nasty Singer 12 it uncovered decals which were totally invisible when starting the cleaning process.
That said, a recently purchased can came with a red and white sticker on the front, reading "NOT FOR USE ON VEHICLES WITH CLEAR COAT" which was rather disconcerting. Otherwise the printing on the can is the same as before. I have used a little product from this new can, and the results didn't seem any different. Possibly car finishes have changed and are less durable?
Dianne in Colorado