Synthetic Oil

U&A said:

Ok, im thinking out loud and processing this. So Bear with me eh.

This piston slap probably will be hard to “fix” with an oil. We may be able to find a way to quiet it but....If it is a problem with someones truck you would think The piston will rock at the bottom of the cylinder regardless of the oil choice.

Piston slap literally is from a bad design. The short explanation (and one example of a possible problem) is the wrist pin is to low in relation the the “center” of the piston (not actual center) So the connecting rod pushes not only up but sideways on the piston. Then the skirt slaps the cylinder wall.

I really need to think about this one. One would think since oil is being sprayed on the bottom of the pistons that an oil that is a bit thicker would cushion the piston during the slap when the truck is warm. But when the truck is cold......?..... I can see two things working against you. You might want a thinner “W” oil to get to the proper places as fast as possible.

But then you have to think ....when the truck is cold your pistons have shrunk. And when they are smaller piston slap is going to be much worse until they warm up and swell inside your cylinder. So a thicker “W” oil may fill the gap better when cold...?

This may be simply an additive solution. And a base stock solution. I would think the superficial but thick protective layer that zinc and phosphorus makes would be a big help to this. And OBVIOUSLY moly as well. Piston slap is such a violent forceful action. So even with a protective oil coating and your additives you’re still going to hear a smack sound.

No different than coating two steel plates with oil and dropping one perfectly flat on top of another. Oil is protecting them from each other but they still “smack”. And being that the surface shapes match each other the oil still creates a protective film.

So just because we’re hearing it does it actually mean the piston and cylinder wall are touching each other? I bet NOT if you are using a good oil. They (piston and cylinder) are both obviously almost identical matching shapes constantly being coated in oil.

Reason I say good oil such as a high-quality synthetic is... conventional’s “wash/wipe” off of the cylinder (and other high friction spots) in some places. A good base stock will be attracted and stay.


That was to much thinking. I need some George Dickel.



Sent while firmly grasping my redline lubed RAM [emoji231]

Click to expand...

tjfdesmo said:

I think the slap we hear is at the top of the stroke. I have pulled apart engines that the skirts showed minor scuffing from slap, but the top ringlands show more wear.

Here's some info from Wiseco on offsetting the wrist pins to help.

https://www.google.com/amp/blog.wiseco.com/what-is-wrist-pin-offset?hs_amp=true

Click to expand...

U&A said:

Ok, im thinking out loud and processing this. So Bear with me eh.

This piston slap probably will be hard to “fix” with an oil. We may be able to find a way to quiet it but....If it is a problem with someones truck you would think The piston will rock at the bottom of the cylinder regardless of the oil choice.

Piston slap literally is from a bad design. The short explanation (and one example of a possible problem) is the wrist pin is to low in relation the the “center” of the piston (not actual center) So the connecting rod pushes not only up but sideways on the piston. Then the skirt slaps the cylinder wall.

I really need to think about this one. One would think since oil is being sprayed on the bottom of the pistons that an oil that is a bit thicker would cushion the piston during the slap when the truck is warm. But when the truck is cold......?..... I can see two things working against you. You might want a thinner “W” oil to get to the proper places as fast as possible.

But then you have to think ....when the truck is cold your pistons have shrunk. And when they are smaller piston slap is going to be much worse until they warm up and swell inside your cylinder. So a thicker “W” oil may fill the gap better when cold...?

This may be simply an additive solution. And a base stock solution. I would think the superficial but thick protective layer that zinc and phosphorus makes would be a big help to this. And OBVIOUSLY moly as well. Piston slap is such a violent forceful action. So even with a protective oil coating and your additives you’re still going to hear a smack sound.

No different than coating two steel plates with oil and dropping one perfectly flat on top of another. Oil is protecting them from each other but they still “smack”. And being that the surface shapes match each other the oil still creates a protective film.

So just because we’re hearing it does it actually mean the piston and cylinder wall are touching each other? I bet NOT if you are using a good oil. They (piston and cylinder) are both obviously almost identical matching shapes constantly being coated in oil.

Reason I say good oil such as a high-quality synthetic is... conventional’s “wash/wipe” off of the cylinder (and other high friction spots) in some places. A good base stock will be attracted and stay.


That was to much thinking. I need some George Dickel.



Sent while firmly grasping my redline lubed RAM [emoji231]

Click to expand...

chrisbh17 said:

That is how I understand piston slap as well. Its also complicated by the fact that Hemi's have short piston skirts, which means the wrist pins are that much closer to the bottom of the piston than the top.

The noise we hear, I believe, is the bottom of the skirt tapping the bottom of the cylinder bore as the piston begins its upstroke. Technically, since the skirt doesnt really "do" anything in regards to compression, etc, it shouldnt be a REAL issue other than noise. Even if it causes wear, its down at the bottom most part of the cylinder bore, a place where the rings will never get to, so even over time it should not really affect the reliability, power output, etc of the engine.

I would think the only thing to really worry about is if it does cause wear, do the wear metals get caught in suspension and/or filtration. We are clearly nuts about oil and filter quality around here, so I would think that is a non-issue for us.

The fact we see (hear?) GM engines with piston slap going for 200K+ miles without an issue leads me to believe it is also a non-issue for us as well. A thicker oil might cushion, like you said, and lessen the noise a good amount, but the slap is still technically there because we cant really change the physics of it all.

Click to expand...

U&A said:

Don’t you lie Mr. !

We know you. You won’t be able to resist some fresh oil for that Florida trip[emoji1787]. [emoji1303][emoji41]


Sent while firmly grasping my redline lubed RAM [emoji231]

Click to expand...

tjfdesmo said:

I think the slap we hear is at the top of the stroke. I have pulled apart engines that the skirts showed minor scuffing from slap, but the top ringlands show more wear.

Here's some info from Wiseco on offsetting the wrist pins to help.

https://www.google.com/amp/blog.wiseco.com/what-is-wrist-pin-offset?hs_amp=true

Click to expand...

tjfdesmo said:

Wiseco has been around a long time:

First, it improves the noise characteristics of the engine due to piston slap at top dead center (TDC). This is a major NVH (noise vibration and harshness) concern to production engineers who want to eliminate alarming noises anywhere they can.

Click to expand...

U&A said:

Can we get a working link?


Sent while firmly grasping my redline lubed RAM [emoji231]

Click to expand...

tjfdesmo said:

Sorry, I tried it on my phone and laptop and it worked.
How about this:
http://blog.wiseco.com/what-is-wrist-pin-offset

Click to expand...

U&A said:

If your truck has been sitting overnight do you guys throw your truck into neutral for a minute before taking off?

I’ve been doing this for the past couple weeks at least. Not every time but most of the time when I go to put my truck into reverse after sitting in neutral for a while the transmission does not have that normal slight clunk feeling.

Seems it may actually be beneficial to get that fluid moving first.


Sent while firmly grasping my redline lubed RAM [emoji231]

Click to expand...

tjfdesmo said:

Sorry, I tried it on my phone and laptop and it worked.
How about this:
http://blog.wiseco.com/what-is-wrist-pin-offset

Click to expand...

pacofortacos said:

I do not, have you lubed your driveshaft splines?

Click to expand...

U&A said:

Ok, im thinking out loud and processing this. So Bear with me eh.

This piston slap probably will be hard to “fix” with an oil. We may be able to find a way to quiet it but....If it is a problem with someones truck you would think The piston will rock at the bottom of the cylinder regardless of the oil choice.

Piston slap literally is from a bad design. The short explanation (and one example of a possible problem) is the wrist pin is to low in relation the the “center” of the piston (not actual center) So the connecting rod pushes not only up but sideways on the piston. Then the skirt slaps the cylinder wall.

I really need to think about this one. One would think since oil is being sprayed on the bottom of the pistons that an oil that is a bit thicker would cushion the piston during the slap when the truck is warm. But when the truck is cold......?..... I can see two things working against you. You might want a thinner “W” oil to get to the proper places as fast as possible.

But then you have to think ....when the truck is cold your pistons have shrunk. And when they are smaller piston slap is going to be much worse until they warm up and swell inside your cylinder. So a thicker “W” oil may fill the gap better when cold...?

This may be simply an additive solution. And a base stock solution. I would think the superficial but thick protective layer that zinc and phosphorus makes would be a big help to this. And OBVIOUSLY moly as well. Piston slap is such a violent forceful action. So even with a protective oil coating and your additives you’re still going to hear a smack sound.

No different than coating two steel plates with oil and dropping one perfectly flat on top of another. Oil is protecting them from each other but they still “smack”. And being that the surface shapes match each other the oil still creates a protective film.

So just because we’re hearing it does it actually mean the piston and cylinder wall are touching each other? I bet NOT if you are using a good oil. They (piston and cylinder) are both obviously almost identical matching shapes constantly being coated in oil.

Reason I say good oil such as a high-quality synthetic is... conventional’s “wash/wipe” off of the cylinder (and other high friction spots) in some places. A good base stock will be attracted and stay.


That was to much thinking. I need some George Dickel.



Sent while firmly grasping my redline lubed RAM [emoji231]

Click to expand...

Fitz-0518 said:

This "knock" issue in the new HD 6.4 engines is starting to be recognized in the better, engaged, higher rep service departments. Our truck groups inside guy says that communications/discussions with FCA/Ram technical support people has focused on this. Reason,,they are seeing more customers bringing in their trucks with this knock. Short piston skirts, bad run of wrist pins (under sized) is what he is hearing. Nothing out on their secure sites yet. Just talking about what they believe is the cause. FCA may do, what GM did in the 90's when they had the same issue. Double the warranty. Many people took that offer and lived with the engine clatter.
I would agree that there is no oil made that can/will address this issue.
One other thing he shared, was the number of factory engine swaps (5.7) they are doing, is now 1 per week. This is on the city and county vehicles that have high idle time relative to miles. Rear of cam fails. "Oil pressure is too low at idle" Our 6.4 2500 engines also have variable pressure oil pump systems. Need to research, can we use a diagnostic tool like Autel 608 or other to change the oil pressure. The "talk" on the net is, a 5psi increase in oil pressure at idle, reduces the risk of oil starvation failure. Need to check out what is fact. Fitz

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chrisbh17 said:

At least on my 5.7L, all I need is 50-100 RPM higher idle and the oil pressure would be much better. Different oils respond differently, though...RL 5-30 at hot idle is upper 30psi, PUP 5-20 at hot idle was upper 20's. But once you get off idle just a little bit, the engine gains 10psi pretty quickly.

On the flipside, pressure being the resistance to flow, we need more FLOW at low RPM, not more PRESSURE. If they are thinking the answer is higher pressure, IMHO that means there is a restriction in the design and getting more RPM to shove more pressure into the system is just a bandaid. The real answer would be to open up the restriction, but my guess is that wont ever happen since it would probably require a redesign of the oil passages, path, etc.

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