piston slap

[wag123]

The noise is coming from the pistons rocking in their bores and is caused by the angular change in geometry from the crankshaft/connecting rod transitions. In the old days they just made the piston skirts longer to minimize the piston rocking and the noise it creates. With the manufacturers trying very hard to squeeze every possible 1/10 MPG out of their vehicles, the friction produced by the longer skirts is one of the things that they had to reduce. The oil you use will only have a minimal affect on reducing this kind of mechanical noise. Some higher end manufacturers are becoming increasingly sensitive to customer complaints about this noise and are experimenting with lengthening the piston skirts and bonding a thick coating of molybdenum to them to reduce the friction, but this is an expensive fix and not economically viable to use in lower priced mass market vehicles.

 

[mobilaltima]

should i try some M1 0W40?

 

[Rick in PA]

Originally Posted By: wag123
The noise is coming from the pistons rocking in their bores and is caused by the angular change in geometry from the crankshaft/connecting rod transitions. In the old days they just made the piston skirts longer to minimize the piston rocking and the noise it creates. With the manufacturers trying very hard to squeeze every possible 1/10 MPG out of their vehicles, the friction produced by the longer skirts is one of the things that they had to reduce. The oil you use will only have a minimal affect on reducing this kind of mechanical noise. Some higher end manufacturers are becoming increasingly sensitive to customer complaints about this noise and are experimenting with lengthening the piston skirts and bonding a thick coating of molybdenum to them to reduce the friction, but this is an expensive fix and not economically viable to use in lower priced mass market vehicles.


Good summary. Reducing the piston skirt would also reduce the amount of mass in motion for a little more fuel savings and I wonder if it allows them to make the block just a little less tall for weight savings.

I was surprised when I looked at a modern piston in a cut-away engine at an auto show. They don't look anything like the pistons I remember. In fact, they just don't look like a piston to me. But it's been quite a while since I had a car engine apart.

My car, a '01 PT Cruiser, has a little piston slap. It goes away in a couple of blocks of driving. I've gotten use to it.

 

[Merkava_4]

Originally Posted By: mobilaltima
should i try some M1 0W40?


More like High Mileage 10W-40.

 

[spk2000]

Maybe mine is not piston slap as i does not go away like many other are saying. How can you be sure it is piston slap.