Quote:
Originally Posted by chiphead
Part of that is the oil weight ratings are a mile wide. Some 10W30s thin out to almost 20 wt, and others are closer to 40wt when they get hot. So if you change oils and the actual viscosity is different, I would expect changes in lifter noise and some small change in hot oil pressure.
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That's why I talked about different additive packages and cold flow properties as being some of the possible reasons.
When I found this out I didn't change viscosity. At least not as they are printed on the labels. I went from 20w-50 Valvoline to 20w-50 Amsoil, and the lifter noise stopped.
I've also run 20w-50 Amsoil with both styles of Comp hydraulic roller lifters with absolutely no noise issues at all which is totally opposite of what everyone says, apparently including Comp, that you need 10-30 in these things.
So it has me thinking it's not really as much about viscosity as it is the type of oil being run.
I'm not suggesting change for anyone, I just know what has worked for us. I know 10-30 would also be just fine, I've experimented with that viscosity in a couple cars. It wouldn't surprise me if other high end brands like Brad Penn or Royal Purple or ??? would work just fine too with the higher viscosities.