Ha, as i was typing that i considered the possibility your car might be a diesel, but decided otherwise….go figure! But ya, as the others have said, there is also diesel stabilizers, but diesel does have a longer life span. Putting a stabilizer in wont hurt anything, so personally, id put it in anyways just to be safe….
They exist. I think primarily a Japan thing (no surprise…). I havent seen one in person, but seen them for sale or some weird bidet article about all the options you can get. Hot/cold water, his/her’s, blow dry, lights, music, multiple user pre-sets, etc. usually it’s sold as the entire toilet, not an “add-on” option.