re: 40W oil

[Tessie McMillan <tessmc@xxxxxxxxxxx>]

Hi Andy! You say that 15-40 operates like 40w at higher temperature...
OK, everyone on this list knows I'm not a mechanical engineer, so I can 
make statements like I'm about to make without impunity. I'll just get 
told "balderdash". &:-) I'm used to that! Anyway, I'm gonna 
argue that 15W - 40 oil is a certain percent 15, a certain percent 30, a 
certain percent 40, etc. I don't understand how the oil can re-chain 
itself to change viscosity with temperature. I'm assuming that portions of 
it work optimally at different temperatures. If that is true, then only a 
fraction of the oil in my engine, when the engine is hot, is operating at 
a high viscosity and therefore able to lubricate the engine well. And if 
only a portion of the oil in the engine is being really effective at high 
temperature, then the engine is under-lubricated and temporarily adding 
more high viscosity oil should help.

I've gotten lots of feedback on this issue off-digest. One point that Russ 
Neely postulated was that a higher viscosity oil might also be harder for 
the oil pump/pickup to circulate. I don't know how to answer that, but it 
is a valid point. Russ, you'll have to chime in here to amplify your 
comment on how the Alfa engines do NOT have the problem that my Quattro 
engine displays, by dint of large oil capacity and construction of the pan 
&:-).

If someone could explain how multi-viscosity oil works, that would be a 
really interesting thread...

Take care -

Tess
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