People have been pouring all kinds of vegetable oil and olive oil down the toilet since marine toilets were invented. The early ones had leather seals etc...and leather soaks up oil, so it made sense...a couple of tablespoons would keep a toilet pumping smoothly for months. Leather eventually gave way gave way to rubber, neoprene and nitril, which doesn't absorb oil, it just washes out in few flushes. But that hasn't stopped people from pouring literally gallons of oil--or worse yet, pricy liquid "head lube" products--down their toilets.
There's a much better way...do it once and it lasts all season: Buy a tube of SuperLube thick teflon or silicone grease (Ace Hardware carries it)--ONLY the thick grease, not the SuperLube spray or liquid. Remove the 4 screws that hold the pump onto the base, lift the pump, stick the tube nozzle into it and put a healthy squirt--at least a tablespoon--into it. Put the pump back onto the base, pump the toilet a few times to spread the grease all over the inside of the pump cylinder and you're good to go for at least 6 months, even longer if you don't use the boat much. Make it part of spring recommissioning and save the Canola oil for salads and cooking.
And btw... the SuperLube grease is ideal for lubing winches, seacocks, y-valves and anything else that needs lubrication. A $6 tube will last you several years.