Best suited lubricants

Get a couple cans of silicone spray (Walmart, hardware stores) and spray every piece of rubber. Door seals, pop out seals etc. any black piece of rubber gets sprayed. You will be amazed at where you may find seals at when you start looking. It will keep them from cracking and leaking. Also good on the toilet seal, when you flush and you can see thru the hole into the tank, spray around in there as well to lube the seal on the flap. Do this when water is off and its dry. Also spray it on the grey and black tank dump valve releases. Pull them out and give them a shot and work them back and forth.