GC and LS1 engine clatter / piston slap

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Sep 25, 2006
South Bend, IN
Last weekend I decided to change out the 0w40 Mobil 1 to GC 0w30. I understand that GC is suppose to be protecting better, but the infamous LS1 piston slap is louder now with GC. In fact, even after the car is up to temperature you can still hear the tapping sounds...especially around 1700 rpm when the engine is revved up and the RPMs settle back to throttle around.

I may be overreacting, but I am little concerned that there is so much more clatter now with the GC. Should I consider switching to something like Amsoil 5w40 European oil?
I have been running GC in my LS1 for two years, but there was no piston slap when I got it (previous owner -- a governmental agency -- ran Texico 10W-30) and none since. It is a little noiser than the cast iron cylinder cases I am used to, but nothing I would call piston slap.

Guess I am one of the lucky ones -- or the previous owner broke it in well. I think they ran the p(&& out of it -- they put in new valve springs just before I got it.
I've never even heard a hint of piston slap at all on my 98 Corvette while using GC. It doesn't burn any oil either. I must have one of the good ones too.
I had a loud audible piston slap in my MI 5W30 when my car was newer. Started using Redline 10W30 (nothing too good for my TA) and the piston slap just about disapeared.
In a fleet service garage they were having trouble with a noise in several Tahoe's that everyone thinks is piston slap, including a Chevy rep. We are in the middle of an experiment on a couple of these vehicles (4 out of 12 have the noise, that is said to not be harmful). At the end of the day we put some Red Line gas additive in each cylinder and turned the engine over a few times with the plugs out, add some more and let it all soak over the weekend while the account had a heart attack over six dollar bottles of red fluid being poured away. It completely fixed one and reduced the noise and changed it to a lower pitch on the other. We found that hooking up a device that alows us to selectively stop a cylinder from firing isolated the noise to one or two cylinders. Those cylinders get filled to the top with the gas additive (ouch). We are still working on this and have no clear cut answer yet. I'm actually concerned about making these statements because in past experiments people have made unkind comments. What we do with our little projects is to try to figure out things for ourselves. So much common knowledge about vehicle maintenance turns out to not be very useful in practice. So, here's your chance to take a shot at one of our adventures in vehicle maintenance. The only answer, so far, is that there is a noise of some kind, in one or two specific locations and we can change the tune.
most people experience a REDUCTION in piston slap with the gc. i noticed a small reduction in my ls2 (although there was not much to being with). that being said, go with what works. m1 0w40 is pretty good stuff, stick with it if your engine likes it.
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