Oil for a turbo...

[John Cassidy/Sallyann Mulcahy <jcasidy@uswest.net>]

Hello Audiphiles!

    The rebuilt 20v engine in my '91 200q is approaching 4000 miles.  It
was suggested by the rebuilder that Valvoline 20w50 racing oil is the
best for break in purposes, and it has been changed at 500 then again at
2500 miles.  The next change, is due at 5500.  What are your educated
opinions concerning the switch to sythetic oil?  Should I wait for more
miles, or can I go synthetic then?  A compression check verified the
rings are fully seated.
    Also, I've been using Castrol Syntech in my '90 CQ, purchased with
80kmi.  I also used it in my '84 4ksq, which was running strong and
burning no oil between changes at 250kmi.  The CQ, now has 99kmi and
burns 1 qt. every 1000 miles.  The listers always refer to Mobile 1.  Is
this a superior product?
    Also, what weights would you suggest?  The car turns only 4000rpms
at 100mph, so extended high speed running is unlikely!  Summer
temperature ranges 50-95 deg. F here in Montana.
    Thanks for any input!

John Cassidy
40 valves
16 CVs
6 differentials
8 rings
6 door handles