Does the 2007 Infiniti M35 requires premium gas, can I use mid grade or regular.

You can use a lesser grade. You won't get the most performance or MPG's. The ECU will retard that spark advance due to knocking which will deliver less power.

Thanks, that's the answer I wanted to hear.

He is right. I have a 2009 M35S and it does fine on 87 octane. i put 93 in it every third tank and i always fill it. Mileage? about 23 @70 on cruise and about 16-17 in town.