Transmission 1-2 shift accumulator piston and spring replacement: Do this simple fix on your 1997 or earlier Mark VIII if you experience shifting problems. It may be a good idea to do it even if you don't have problems yet, as the bore gets worn from the original parts. Click this link for instructions and part numbers: accumulator replacement.
Tire Dressing: Do not use Armor-All or similar protectorants on White, Pearl colored or other light colored Mark VIII's. The protectorants dissolves the pigments in the tire. When the tire rotates it can spray the preservative with the dissolved pigments onto the paint. This causes brown yellow stains that cannot be cleaned off because they penetrate deep into the paint. The only recourse is to repaint the section. This warning has been posted for other cars such as the Pontiac Grand Prix, and probably applies to all light colored car. Mudflaps may partly protect the cars finish, but is still advisable to to avoid tire protectorants They have questionable efficacy anyway. Some have reported premature aging and cracking of tires when using Armor-All and other silicone based protectorants.
Thanks to Sandy "Sandyboy" Block and Alexander Sosiak for this information.
Rust Areas: The 1/2 inch thick sound deadening insulation behind the the plastic inner fender shield behind the front tires holds water and collects road debris such as leaves which can form acids when water logged. It is probably best to cut out the lower six inches of this insulation and replace it with a stiff plastic sheet. This area should be cleaned out at least twice a year to prevent rust.
The rocker panel in front of the rear wheel has been reported to rot through from the inside out. It looks like there's an approximately 3/4 inch alignment hole in the sub-frame which allows water, salt, sand, and dirt to work its way up and settle INSIDE the rocker panel. This area should be checked and cleaned out frequently. If possible a rust sealer should be sprayed inside this area.
Thanks to Chad "Chadricco" Nordling and Alexander Sosiak for this information.
Rear Sway Bar: The rear sway bar is prone to break just to the left of the right rear bushing. The reason for this is that the sway bar is hollow. Water can get in through the ends, and rust the tube from the inside out. Sealing the ends may help. The alternate is to replace it with an aftermarket solid sway bar.
Thanks to Dave C, Adam Neilson and Chad "Chadricco" Nordling for this information.
Collector's Edition Interior Door Script : The gold inner door script is prone to wear away easily. It is just gold ink pad printed onto the gloss wood panel. Just touching it damages it. Do not touch or wash this script. If an arm coated with suntan lotion touches the script, it will instantly be transferred to the arm. Some owners report their script wearing away in less than a year or 10,000 miles. This wood panel cannot be obtained separately, it must be ordered as part of the entire door panel. It should be replaced under warranty.
Passenger side script shown (because the driver's side wore off!)