LS1 Piston slap quandary

[NutBuster]

My 1998 Z28 has 169K on it and does tend to get the well known piston slap noise on some cold startups. In the past couple years, I've tried about 8 different types of conventional and synthetic oils to see which ones help the noise the most (all have been 5-30).

What I've noticed is that synthetics seem to be the worst at controlling the noise. The only exception was PP 5-30, which controlled the noise nearly 100% of the time until I had about 3k miles on the oil. Almost overnight, it went from great to awful.

The two best conventional oils were Castrol and Shell.

The WORST oils at controlling the noise have been M1 and QS synthetic.

My question is this...what is it about synthetics that make them so incapable of controlling the noise? Are synths so slippery that they can't cling to the cylinder walls overnight? Has anyone ever done an experiment to test the "clinginess" of oil on metal? I figure a drop of various oils on a vertical piece of iron might give an idea of that particular property.

Anybody else out there with this same problem?

 

[Merkava_4]

Quote:
I've tried about 8 different types of conventional and synthetic oils to see which ones help the noise the most (all have been 5-30).


You should have tried 8 different viscosities instead; it's not the brand that's going to make the difference; it's the viscosity. Try an SAE 30 or a 10W-40 to start with.

 

[Bobert]

I think there is a difference with brands and sometimes very noticeable. I know our administrator G-MAN has recommended Castrol conventional for piston slap. I remember he said Castrol Start-up was the best, but that is now discontinued. Syntec Blend, and Castrol High Mileage are other oils high on the list to try. Regular Castrol is also supposed to be good.

High Mileage oils are most likely going to have better cling due to the small percentage of esters, so High Mileage Castrol might be the first to try.

Some synthetic blends seem to do well at quieting noise-- Syntec Blend and Valvoline Durablend.

As far as synthetic, many people mention that Redline makes their engines nearly silent, but it's too pricey for most.

 

[BuickGN]

Running forged JEs in the GN, I have piston slap for the first minute and I've run into the exact same thing. I run a thick dino oil over a synthetic. Noise is reduced as well as wear and tear on the pistons, rings, and cylinders.

 

[Merkava_4]

I'd make up my mind to what brand I wanted to go with, then I'd start trying different viscosities until the noise subsided or went away entirely.

 

[mechtech2]

Nobody knows why. M1 is good oil, but it probably takes the trophy for the most extra noise.
Maybe it is because synthetics are very consistent in their molecule sizes, vs. many different sized molecules in dinos. Certain vibrations will pass more readily and not be dampened.

 

[tackleberry625]

Originally Posted By: Bobert
I think there is a difference with brands and sometimes very noticeable. I know our administrator G-MAN has recommended Castrol conventional for piston slap. I remember he said Castrol Start-up was the best, but that is now discontinued. Syntec Blend, and Castrol High Mileage are other oils high on the list to try. Regular Castrol is also supposed to be good.

High Mileage oils are most likely going to have better cling due to the small percentage of esters, so High Mileage Castrol might be the first to try.

Some synthetic blends seem to do well at quieting noise-- Syntec Blend and Valvoline Durablend.

As far as synthetic, many people mention that Redline makes their engines nearly silent, but it's too pricey for most.


Just curious, why was the Castrol Start UP discontinued??

 

[Triple_Se7en]

Poor sales was the reason Castrol Startup was discontinued.

I would recommend trying a name brand 10W-30 conventional or syn-blend.

 

[PT1]

I have the same issue and a 50/50 mix of PP or Mobil1 10w30 & 5w30 has cured my startup noise.

 

[tackleberry625]

Originally Posted By: Triple_Se7en
Poor sales was the reason Castrol Startup was discontinued.

I would recommend trying a name brand 10W-30 conventional or syn-blend.


cool thx

 

[Tree Hugger]

Originally Posted By: Triple_Se7en
Poor sales was the reason Castrol Startup was discontinued.


May not have been unconnected to the fact that their advertising copy stated very clearly "most wear on your engine occurs with startup"...

I know what they mean, but they explicitly state that their product is responsible for wearing out your engine?

 

[bluesubie]

Auto-RX seems to have made the biggest difference in quietening my wife's '99 Outback. That MY is known for noisy lifters.

In the past I have tried M1 5W30, Havoline conventional 5/10W30, Syntec Blend 10W30, GTX 5/10W30, GTX Start-UP 10W30 and Valvoline conventional 10W40. I was surpised that the 10W40 wasn't any quieter than any of the xW30's.

There is currently 1 quart of Syntec 10W40 with 3.5 quarts of GTX 5W30 in it now. I don't know if it's this combination that made it better, or the Auto-RX. The Syntec is only in there because I thought I would need to top off my car on a road trip this past summer, but I didn't need to use it.

-Dennis

 

[tackleberry625]

Originally Posted By: Tree Hugger
Originally Posted By: Triple_Se7en
Poor sales was the reason Castrol Startup was discontinued.


May not have been unconnected to the fact that their advertising copy stated very clearly "most wear on your engine occurs with startup"...

I know what they mean, but they explicitly state that their product is responsible for wearing out your engine?

lol true.....if you look at it from that point of view. I'd never use that oil because it would wear out my engine faster, haha

 

[Rock_Hudstone]

Originally Posted By: NutBuster
My 1998 Z28 has 169K on it and does tend to get the well known piston slap noise on some cold startups. In the past couple years, I've tried about 8 different types of conventional and synthetic oils to see which ones help the noise the most (all have been 5-30).

With that high mileage and the piston slap I'd suggest a 15w-40 HDEO oil. Shell Rotella is one of the better choices.

5w-30 is too thin even under the best of circumstances, especially in a temperate climate like Georgia.
Moreover, it is not recommended for any special abilty to prevent engine wear, but rather to help manufacturers satisfy their CAFE mileage requirements.

 

[Merkava_4]

Yes I agree, I'd be throwing some kind of thick oil at those pistons to shut them up; and if I really wanted to get ornery, I'd throw some SAE 40 at them.

 

[Huhwhye]

Originally Posted By: bluesubie
Auto-RX seems to have made the biggest difference in quietening my wife's '99 Outback. That MY is known for noisy lifters.

In the past I have tried M1 5W30, Havoline conventional 5/10W30, Syntec Blend 10W30, GTX 5/10W30, GTX Start-UP 10W30 and Valvoline conventional 10W40. I was surpised that the 10W40 wasn't any quieter than any of the xW30's.


-Dennis


I think the reason for his noise is different than yours.

Autorx is not going to fix poor manufacturing tolerances.

I'd run Rotella and drive it until it breaks. Then rebuild using good aftermarket pistons that are a matched set (unlike factory) and actually machine it correctly and measure tolerances (unlike factory).

I know people that have 200k plus on a piston slapping motor. Sounds like a bucket of bolts but still runs great.