My 99 outback with 120k miles has, for the last 50k or so, sounded like a diesel. My mechanic said he was pretty sure it was the shims in the cylindars (I may be getting this wrong now) and that to fix it was a lot of work and results far from guaranteed. He says no damage is being done and I can live with the noise, but it is irritating and anyone riding in my car tends to wonder what is going on.
Any ideas what to do?