So my 2013 Infiniti G37 requires premium gas (91 octane) but I just got it so I didn’t know, and I accidentally put regular gas (87 octane) into the car.
I filled my tank almost fully with regular gas. I have only done this once since I just got it, and I plan on using premium gas in the future.
I am not an expert in cars, but I am worried that my car might be permanently damaged from this. Is this true or do I not have to worry if I only do this once?
It isn't going to matter in the long run and shouldn't cause you any issues to run the car with the tank of fuel you put in if that's what you decide to do.
Cars don't have an octane sensor. What they have is a knock sensor. When octane is too low (or for other reasons) and things go bump in the night (ping or knock), the knock sensor picks this up and pulls ignition timing to make the ignition cycle occur later in the revolution. This has the unfortunate side effect of reducing power. The car pulls timing so the low octane fuel won't damage the engine. As long as you don't push your car (think easy driving), it shouldn't have an issue.
Luckily, there is a way to fix your issue without having to drive it very much. There are octane booster additives which you can use right away which will solve your issue. Drop in a can/bottle and you should be good to go with no worries.
I had a G35. I believe there was language in the owner's manual that said regular gas would not hurt the engine but you would not get full performance.
