can you safely put 89 octane in an infiniti fx35 ?

It would be best to put the premium fuel in it the engine in your FX35 is Nissan's VQ 3.5 v6 engine which is a high compression engine. I have 2 cars with that motor one is a 03 Maxima and the other is a 05 G35. put cheap gas into these engines will rob your HP and gas mileage as well. I made the mistake of putting cheap gas in my Maxima after that the car started running ruff and my service engine light came on I got lucky that all I needed to do was run 2 synthetic fuel injector cleaners thru it and keep putting good gas in it. You can put the crappy gas if you like but in the long run it will cost you. Hope this helps

You can use regular octane fuel in the fx35 just fine. There is no need to use anything more. It is not a performance engine with high compression or supercharged which is the only reason to put higher octane fuel in the car or truck.

why couldn't you? I'm pretty sure those don't have real high compression engines.