>  I use 5w-30 here in the winter. This is just about right when the high
> > temperature for the day is in the single digits and still has a minus sign in
> > fron of it.
>
> Yeah, and if you ran that stuff here in Texas in the summer your oil
> preasure wouldn't make it out of single digits!
TBill (Treasury Bills?),
I run 10-30 Royal Purble w/Prolong (Houston area). No problems. I have
no pressure guage, but certainly the oil light would flash if it fell
below 10 PSI. Film strength is the key, the new synthetics can maintain
fantastic film strength at very low viscosities, and I think the Prolong
does help. So even though pressure may fall off due to lower viscosity
in hot weather and hotter engine temps, the fantastic film strength
remains and therefore the engine is well protected.
Most of the guys on the Drag Strips and elsewhere in the performance
community are using 5w/whatever and are heading toward 0w/whatever. And
they have a few dollars in thier engines (100Ks?). They have the data
and use the lower vis synthetic.
Regards
Mark B. Magee
87GL
82 Diesel Westy
Kemah TX