I've got a stainless PPK/s. I use Tetra cleaner/lube spray on the internal springs/pivots. This product cleans and then leaves behind a light oil that is fine for this area, which does not see lots of heavy-duty rubbing.
I use Tetra grease on the portions of the frame and slide that mate with each other. This is an area where light oils are not enough. A regular gun oil would do ok here too, but does not stay in place as well as a light grease. There are a lot of good gun greases out there - but I use Tetra since I can find it locally.
I also use regular gun oil where the barrel/lug and slide touch each other. Pistol runs just fine...