Here, allow me to repeat myself, in case it didn't register the first time around:
So, sludging is a broader problem than just low oil operating temperatures.
Here is one of the current lists of sludge engines, it's not just short trips that promote the formation of sludge:
The following engines were reported by their manufacturers to have a problem with sludge accumulation:
1998-2002 Chrysler 2.7 L LH V6
1998-2002 Dodge Stratus/Chrysler Sebring
1998-2002 Dodge Intrepid/Chrysler Concorde
1998-2003 Saab H engine B204/B234 I4
1998-2003 Saab 9-5 B234 2.3 L
1999 Saab Viggen B234 2.3 L
2000-2002 Saab 9-3 B204 2.0 L
2000-2003 Saab 9-3 convertible B204 2.0 L
1996-2001 Toyota 3.0 L 1MZ V6
August 1996-July 2001 Toyota Camry
June 1998-May 2001 Toyota Camry Solara
July 1997-May 2001 Toyota Sienna
July 1996-May 2001 Toyota Avalon
November 2000-July 2001 Toyota Highlander
August 1998-July 2001 Lexus ES300
January 1998-July 2001 Lexus RX300
1996-2001 Toyota 5SFE I4
August 1996-July 2001 Toyota Camry
June 1998-May 2001 Toyota Camry Solara
August 1996-April 1999 Toyota Celica
1997-2004 Volkswagen VW 1.8t I4
1997-2004 Audi A4 1.8t
1998-2004 Volkswagen Passat 1.8t
http://en.wikipedia.org/wiki/Oil_sludge