Don:
You'll get PLENTY of opinions on this. On my new 455HO my machinist specified Mobil 1 5W30 for the dyno break-in and pulls. That's also what I'm planning to run in it for good - unless my OP gauge "tells" me I need a higher viscosity rating.
Later,
Lloyd
'72 Formula 400 - soon to be a 455HO, TH400, A/C, etc.; Lucerne Blue with Medium Blue Interior
Restoring a '72 GTO 455HO, TH400, A/C, etc.; Sundance Orange with Parchment buckets
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Regards,
"455HO" Lloyd
2008 GMC Sierra Denali 2WD Crew, L92 6L80E, Silver w/ Ebony guts, 14.26 @ 98
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