If you know someone/somewhere that has silicone fuser oil for a xerox copier , I've found it to last the longest. It is more of a grease than an oil.
Put some on a cloth and wipe a thin film on the gaskets.
DO NOT spill any on a floor. It's extremely slippery and almost impossible to clean up.
Silicone spray is not the same and only lasts a short time.
I did tire shine on mine, and it lasted a month or so before it was back to the faded look. It actually looked really good. Keep in mind: There is a metal piece under the rubber on the windows, and once that starts to corrode, no amount of fancy lubrication is going to make the spots go away. common opinion is to replace that piece entirely. That is on the window trim though, not on the rubber strip between the door and the cab.