Do Piston Rings Adjust to Different Oil Viscosities ?

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922
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Ontario , Canada
Like many myths when it comes to oil wisdom, you often hear people say not to change oil viscosities on an engine as the rings get used to a certain viscosity. Just wondering how true that might be ?. Personally I think the difference between oil viscosities in terms of actual cylinder wall thickness would be very minute and any good operating piston ring should be able to exert enough pressure on the cylinder to overcome thickness issues - unless the rings are frozen in place due to sludge/varnish. I've been runing 5w-30 on my engine for the past 9000 miles since new (Castrol GTX and Mobil1 5w-30), but I'm just switching to Redline 5w-20 now to test it out. I'm hoping the 5w-20 doesn't seep past the rings too easily. Any opinions on this subject - myth of fact ?. thanks Joey
 

Jay

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1,607
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Idaho Falls, ID
The rings had better be able to adjust to differences in viscosity because viscosity varies greatly according to temperature. For example, at 32*F M1 5w-30 will be about 400cSt. The HTHS of Redline 5w-20 is slightly higher than M1 5w-30 and so will be slightly thicker at the ring/cylinder interface at operating temps. Incidently, I'm running M1 0w-20 whose HTHS is significantly lower than Redline 5w-20 and M1 5w-30 with no measurable oil consumption after 1000mi. [ May 04, 2003, 12:39 AM: Message edited by: Jay ]
 

Idrinkmotoroil

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922
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Ontario , Canada
quote:
Originally posted by Jay: The rings had better be able to adjust to differences in viscosity because viscosity varies greatly according to temperature. For example, at 32*F M1 5w-30 will be about 400cSt. The HTHS of Redline 5w-20 is slightly higher than M1 5w-30 and so will be slightly thicker at the ring/cylinder interface at operating temps. Incidently, I'm running M1 0w-20 whose HTHS is significantly lower than Redline 5w-20 and M1 5w-30 with no measurable oil consumption after 1000mi.
that makes sense, good info Jay. The Mobil1 5w-20 sounds like it is working well for you, it'll probably be a few more months until we get it up here. I'd be interested in seeing a UOA on that oil, hopefully I'll have one on the Redline by mid June. Good info to share since we have the same engine for the most part. [Cool] Joey
 
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