2001 C5 Vette Recommendation

Patman · Mar 25, 2003

How could oil not fix it? Or at least mask it so you wouldn't hear it. With a thicker oil, the piston won't slap around in there as easily.

How about this scenario. I had piston slap in my 94 Grand Am GT (3.1 engine) I found that if I started up the car stone cold, moved it onto the street in front of my house, and then shut it down, that if I started it up 8 hours later, there would be no piston slap at all. I always wondered why that was, but I figured it out now. When it was started up cold, it would move some thick oil around, and since I never heated it up fully, that thick cold oil would stick to the parts, not drain back to the pan like it did when it was shut off hot. So then on that restart, voila, no piston slap.

buster · Mar 25, 2003

Have the results been been on par with M1? Did you order the Amsoil or buy it retail?

vettenuts · Mar 25, 2003

Busre, I am fortunate to have a local seller of Amsoil. The case of gallon jjugs equates to $5.20/quart. My analysis can be found in the used oil analysis section with a search. I would find the link but am away from home using a PDA so comms arre quite slow.

Norm Olt · Mar 26, 2003

Mike says: "You need to let GM and Ford in on your discovery. It could solve all their problems with the annoying knock aka piston slap."

I always thought they were two totally different & unrelated manifestations?

Well, maybe they SOUND alike to some people...?

buster · Mar 26, 2003

What about M1 0w-40 for a Vette? This oil has shown great results. It might thin a little, but it would still be a high 30wt. oil and much heavier then M1 10w-30.

tai · Mar 26, 2003

Please help me understand something. Why is the piston slap occurring only at startup? And if it's only occuring at startup, why does the hot temp viscosity more important than the cold temp vis? By that, I mean if the oil is too thin at startup, using a 10w-30 or a straight 30w instead of a 0w-30, 5w-30, or even 0w-40 would be better for the noise, right?

Patman · Mar 26, 2003

quote:

Originally posted by buster:
What about M1 0w-40 for a Vette? This oil has shown great results. It might thin a little, but it would still be a high 30wt. oil and much heavier then M1 10w-30.

I think 0w40 would work excellent in the LS1. I've been recommending to many LS1 owners to try it, especially if they burn oil.

Patman · Mar 26, 2003

quote:

Originally posted by tai:
Please help me understand something. Why is the piston slap occurring only at startup? And if it's only occuring at startup, why does the hot temp viscosity more important than the cold temp vis? By that, I mean if the oil is too thin at startup, using a 10w-30 or a straight 30w instead of a 0w-30, 5w-30, or even 0w-40 would be better for the noise, right?

Mobil 1 0w40 is thicker when cold than their 10w30, at least in summer temps. It's 40c viscosity is thicker by almost 20cst. The only time 0w40 is thinner than 10w30 is in extreme cold weather.

buster · Mar 26, 2003

I think so too. It has shown really good numbers in the analysis section. Thanks.

Mike_dup1 · Mar 26, 2003

quote:

Originally posted by tai:
Please help me understand something. Why is the piston slap occurring only at startup? And if it's only occuring at startup, why does the hot temp viscosity more important than the cold temp vis? By that, I mean if the oil is too thin at startup, using a 10w-30 or a straight 30w instead of a 0w-30, 5w-30, or even 0w-40 would be better for the noise, right?

Because the piston is cold. As the engine warms up, its expands in the bore and the noise goes away.

We have been doing some experiementing here with pistion slap. Its not scientific but we have noticed that the ambient air temp has an effect on the amount and duration of the piston slap. For instance, when cold (cold here is below 20 F) the noise is loud and lingers for anywhere up to 15+ minutes. But when the temp is in the 50's or above the noise is light, sometimes not discernable and will disappear in a few minutes.

So I would conclude that depending on where you live, the noise could be different. And that might explain why some feel changing viscosity and or brands of oil has an affect.

Now this is personal experience with my GM truck and the GM trucks of several of my friends over the last few months of winter. All of them have the noise improved with the warmer weather, not with changing the oils. At 50 F I only hear it for a few minutes, but at 0 F is lasts for 15 + minutes.

[ March 27, 2003, 09:21 AM: Message edited by: Mike ]

Nosmo King · Mar 26, 2003

In my 40 years experience mucking around with motors I have found that viscosity of oil and piston slap when cold are related and the 'Noise'
assosiated with piston slap can be reduced with diferent viscosities and brand of oil.

I am new to synthetics ( one year ) but so far
they seem to be more suseptable to engine noise problems ,especialy the new thin ones.

mracer · Mar 28, 2003

Ford must be the stupidest company on the face of the earth. A few years ago they had a piston slap problem on some 99 Lightnings. They were replacing these $5000 engines when all they had to do was change the oil.

My GOD...heads will roll if this gets out.

PS. Please don't tell anyone in Detroit

buster · Mar 28, 2003

I would think 0w-40 and D1 would be the best choice for a C5 in the Mobil line up. I'm surprised more people dont use D1 for high performance engines.

Mike_dup1 · Mar 28, 2003

There must be 101 solutions for piston slap?

I know someone with a new Ford F150 and he says he has piston slap on is V8 engine.

Its actually a common occurance, most people don't even know its happening. My neighbor has a new Ford Taurus and when she drives away in the AM I can hear the engine noise. I am sure she pays no attention and I would not dare to mention a thing. I came out of the post office the other day and a new Honda Accord just started up as I was walking buy, engine noise that sounded like piston slap to me.

I was talking with a life long friend who has had his own repair shop since the 70's. He tells me they all make this noise, very common. Most only last a few seconds but some last longer. He hear's it day in and day out, has 1 of the few remaining full service gas stations around.

[ March 29, 2003, 09:47 AM: Message edited by: Mike ]

ajax · Mar 29, 2003

oil has not fixed my ls1 p.s.,i have p.s. at 2rpm when car is warm.

vettenuts · Mar 30, 2003

Recently switched my Pontiac Grand Am 3.1 from Mobil-1 to Amsoil. Oil pressure is better but cold start noise is the same.

Bror Jace · Mar 30, 2003

Mike, your post from the 27th was right on. It seemed with my car (Honda Civic) the colder, the louder the noise and the longer it persisted. This did this with both Mobil 1 (5W30 or 10W30 Tri-Syn) and Valvoline Synpower (5W30).

My father, who likes to bust on me for driving a furrin' car, came over to me one cold winter morning after I had just fired up my Civic, laughed and said the car sounded like it was trying to throw a rod. It pissed me off at the time but he was right.

HOWEVER, I have to say that switching to Red Line 5W30 a year later quieted the car right down. The noise all but disappeared.

I am not going to pretend I know why. The two culprits I suspect are either the molybdenum (especially the heavy 600ppm dose) and/or the polyol base oil and its polar affinity for metal.

The car went on to develop a coolant leak and then got torn apart in order to fix that. It has developed some other noises since the "rebuild" so I can't really comment what effect switching from Red Line to Schaeffer Supreme 7000 had (both 10W30 and then 5W30 in winter). The noises seem different so I suspect the Schaeffer was helpful as well. Just too many variables during that last year of operation to be sure.

--- Bror Jace

2001 C5 Vette Recommendation

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