what is the recommended oil for piston slap? will a thicker warm oil help...10/40? or a thicker cold oil 15/30 or 20/40? any one lost an engine after piston slap developed?

 

Well, here's the latest, and hopefully that last bit of news for this thread. I had the dealer go ahead and just do the HG replacement. It cost $1688 including machining the heads.As far as the knock is concerned.... yes, there's a knock. However, it seems to me that it is more of the piston-slap variety rather than bad bearings. It's worse when the engine is cold. It doesn't completely go away after fully hot, but it's not as noticeable. Oh, well. I think I might change over to Mobil 1. Maybe that'll help a bit.

 

Thanks again for everyone's advice!

Piston slap is with most Subes on a cold start-up. Not terminal, but slightly annoying 'cause it sounds like a Diesel!

 

 

I would suggest a 10W-40 oil as the best cure. Shell "Helix Plus", for example.

 

M1 is a good oil, and the 5W-50 oil will be good to use, but it's relatively thin at low temps and will slap more than Helix.