Kind of a worthless thread I guess but something I just noticed. My grandma has an 02' Chevy Trailblazer LTZ that just crossed 100k miles on it. Every time except this last OCI it has what I thought was the notorious piston slap at first. I would always fill it with the correct 7 quarts (it's a 4.2 I6) and it had a tick for 5 minutes or so while I let it idle after changing. I do yearly OCIs, every August I change the oil. She only drives 3-4,000 a year and it does get it's legs stretched out often, not always short trips. My first 2 OCIs I did on it was Castrol GTX 5w30 and a Wix filter 3rd one (last August) was Chevron Supreme HM from my stash, 5 quarts of 5w30 and 2 quarts of 10w30 and a Wix filter This one was a 5 quart jug of Castrol GTX 10w30 I got for free from a neighbor (sealed) and 2 quarts of GTX HM 10w30 from my stash. The major difference with this OCI is I used a Fram Ultra oil filter. There was no "piston slap" at startup and I've driven it since and it hasn't made any noise at startup. This car when sitting overnight would have the "piston slap" for about 5 seconds at startup. When I say piston slap it isn't a loud knock, just a faint noise, not something that I'm concerned about as far as knocking. Am I imagining things or could the oil filter have helped?