High Compression vs.Low Compression engines

[Bill J.]

Does a higher compression engine benefit more from an oil that has a higher HT/HS (high temperature/high shear) rating, vs. a lower compression engine? Street engines, not racers. Does the higher compression cause more of a shearing effect on the oil?

 

[Idrinkmotoroil]

I don't exactly know about shearing itself, but higher compression engines put more stress on the rod bearings, and have higher combustion chamber temps for the most part. I would expect these two features to put more stress on an oil and engine, thus I would prefer an oil with higher capabilities in those departments to improve cooling and have stronger viscosity in the bearings.

 

[MolaKule]

Higher compression engines generally have greater ring tension which places higher radial loads on the cylinder wall, creating more shear on the oil.

 

[VaderSS]

I think other factors come into play. The LT1 has a 10.4:1 compression ratio and is easy on it's oil.

 

[jason07-1zzfe]

My engine is only(?) 8.8:1 and I managed to rip up M1 15w50 pretty nicely.

 

[DABEAR95]

My engine is 11.5-1 and I'm using Castrol 5w30 for the first few thousand break-in miles. I will post the oil analysis after I change the oil for the 2nd time. Then I am going to switch to synthetic for 2 oil changes, sampling the 2nd change to determine which oil shows better results. Should be interesting... Jason Edit for typo [ January 16, 2003, 01:31 PM: Message edited by: DABEAR95 ]

 

[MolaKule]

Vader, True, the L series have higher sump capacities as well which keeps the oil temp moderated.