I put about a half a cup of clean cooking oil in weekly, it keeps everything operating smooth.
Half a cup ??? You're wasting all but about a tablespoon 'cuz anything thin enough to be poured down the toilet washes out in just a few flushes--which is why your toilet needs it weekly...and you're putting an oil slick on the surface in the holding tank, which suffocates the aerobic bacteria needed to prevent odor.
The practice of pouring oil down the toilet to keep it lubricated originated with the first manual toilets...the "innards" that are now rubber were all leather (and still are in the best manual bronze "thrones")...leather soaks up oil. A good dose of it lasts for months. But rubber doesn't...as I said above, it just washes in a few flushes, creating a never ending job to keep the pump lubricated. It never occurs to anyone that there's any other way to do it.
In fact, there's a MUCH easier way that lasts at least a season for most "weekend warriors." Ever notice that most brand new toilets don't need any lubrication for at least a year, sometimes even two years? That's because the pumps leave the factory slathered in thick teflon or silicon "waterproof" grease. Replacing it annually as part of spring recommissioning is easy: Buy a tube of SuperLube thick teflon grease (ONLY the thick grease in the tube...NOT any of the SupeLube liquids or sprays. Ace Hardware carries it it you can't find anywhere else. If your toilet is a jabsco, take the top off the pump...if it's a Raritan PHII/PHC, remove the pump from the base. Stick the nozzle on the tube into the pump and give it a HEALTHY squirt. Put the top back on or put the pump back on the base...pump a few times...you're good to go till next year.
And btw...That tube of SuperLube grease is also good for lubing winches, seacocks, y-valves and anything else that stays wet.