02 Envoy noisy w/Motorcraft 5w30.. ??

[GMorg]

Higher viscosity for a noise only present when cold makes no sense to me. Noise present when oil is thickest. Noise goes away when oil thins.

I did the promised experiment. Drained 450 ml of oil. Now running less than 3.5 quarts in a 4.5 quart system. No noise on the hill this morning.

 

[Blue99]

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...would switching to Trop Artic 10w30 semi syn quiet the engine down???

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This would probably generate the same results as Motorcraft. TropArtic & Mororcraft are very similar formulations, without any significantly higher levels of AW or friction modifier additives.

Look for an oil with higher levels of friction modifiers & viscosity improvers as an aide for noise.

Again, Havoline 5w30 is an option with the 300-400 ppm of moly. Also, a high mileage oil such as Pennzoil High Mileage, is worth a try, especially with spring & warmer temps on the horizon.

Also, VSOT is an option at the 1/2 bottle treat rate. It appears to be highly friction modified and has a good dose of moly.

 

[Rickey]

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Originally posted by GMorg:
Higher viscosity for a noise only present when cold makes no sense to me. Noise present when oil is thickest. Noise goes away when oil thins.

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If it's piston slap the noise is a function of piston to cylinder wall clearances when cold. Therefore a more viscious lube in the gap between piston and cylinder will tend absorb some of the piston's rocking motion and dampen the noise as the con rod thrust angle reverses at TDC and to a lesser degree at BDC.In other words it's not about more flow but rather the ability of the oil to stay put,and not being squeezed out. The noise goes away when the pistons expand from getting hotter. A thinner oil will not be of any benifit in cases of noise caused by clearances. Think of it this way if the pistons clearance remained loose to the same degree even when fully warmed up the slap would become even worse because the oil thinned out. Yes I am firmly in the "thinner is not allways better" camp. Rickey.