I've noted a few comments on oil type & viscosity solving piston slap. My daughter's new (last Spring) Dodge Neon exhibits piston slap on cold start up, but quiets down once warmed up. Car has almost 5K miles and runs fine other than this issue. I broke it in on Castrol 10W-30 GTX last summer, and it currently has M1 5W-30 in the crankcase (I'm in Michigan winter weather). Options are: 1) Take it back to the dealer, complain and maybe get a new short block under warranty; but, risk shoddy workmanship of rebuilding a new engine, or 2) Try to quiet it down with a premium oil mix. Any thoughts? How damaging is piston slap if I let it go?