I e-mailed AC Delco and here is their response:
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Thank you for writing ACDelco.
The PF59 is the same as the PF58 except that it has an antidrainback valve.
The antidrainback valve keeps a slight amount of oil in the engine for
start up. We recommend asking for the PF59. No other manufacturer has a
PF59. They have a version of the PF58, and may cross reference that as
'close enough.' The PF59 is relatively new and because the Silverado and
Sierra were the only vehicles that originally called for this filter, you
may have a bit of difficulty finding one. If you are unable to find a PF59
at your local ACDelco facility, a GM Dealer can always order one for you.
Thank you for your interest in ACDelco.
ACDelco Customer Assistance
Subject: ACD - ACDelco - Other Suggestions
11/30/2002 06:07
PM
-----------------------------------------------
Thank you for writing ACDelco.
The PF59 is the same as the PF58 except that it has an antidrainback valve.
The antidrainback valve keeps a slight amount of oil in the engine for
start up. We recommend asking for the PF59. No other manufacturer has a
PF59. They have a version of the PF58, and may cross reference that as
'close enough.' The PF59 is relatively new and because the Silverado and
Sierra were the only vehicles that originally called for this filter, you
may have a bit of difficulty finding one. If you are unable to find a PF59
at your local ACDelco facility, a GM Dealer can always order one for you.
Thank you for your interest in ACDelco.
ACDelco Customer Assistance
Subject: ACD - ACDelco - Other Suggestions
11/30/2002 06:07
PM