5w-20 in the s2k?
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Joined: May 2011
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From: Indianapolis
30 weight typically shears down to 20 as its in the S2000's engine; I'm not sure I'd want to start at 20 weight and let it shear from there. Will a 20 shear down or is that the happy point for oil in the engine? 30 weights shear to 20 and other UOAs i've seen show no wear problems, so maybe 20 new is okay, but if it were me I'd want some proof.
Are you sure it is shearing that makes it look like a SAE 20 though? It is pretty common for gas engines to have between 1-3% of fuel in the oil (especially in cars with heavy right footers) and that of course thins the oil. More than that in cars with mechanical issues. Not sure what Blackstone uses, but I get my fuel by GC (Gas Chromatography) Also, have you looked at the lube when it was new to see the starting Vis? For example, in another car I was using a popular brand synthetic 5w-50 (huge range I know) and brand new from the quart it is in the 14 cSt range, typical for an SAE 40. After some fuel dilution and perhaps shearing it nearly looks like an SAE 30!
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babylonking11
S2000 Engine Management
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Apr 10, 2013 02:42 PM