Her burning question is whether she can switch from using premium fuel to mid grade. Any mavens out there?? Thanks.

yes she can because with todays modern engines we can switch the fuel with out hurting the car the computer will adjust the timing and things like that slightly to compensate for the lower octane fuel

Read the owners manual it should say on there what type if gas you should be using.

l say go for it but only with chevron or shells gas as long as it does not make a knocking sound it sound be straight.

If your car says on your gas cap premium fuel only then you should use premium only. Switching to anything less will net you less horsepower and worse mileage, it may also cause your car to ping. Some cars are designed to handle both i.e. Jettas but you can try switching and if you do not feel a difference it wo not hurt your engine. The fuel will just burn up faster.

The important factor here is to stick with the fuel that is needed for the car,with anything in life if its been made to work with a certain product then that is what it needs.
Myself have driven Japanese cars for years & performance models.
Some people will say it will be fine & cause no problems yes the ecu will change to the new fuel but it does not mean it not causing harm .But with a decent car why risk putting the wrong fuel in,myself added a lower grade fuel to a car a few years ago l had nothing but trouble with it after.But a week back on higher grade it was running a lot better.
So yes u can run a car on lower fuel grade to save a few pennies,its ur risk no matter what anyone says u ask 99% of performance car owners they will say go with what the book says.You may have no problems & enjoy the car for years or u could have car troubles & the pennies u have saved now r for the repairs.

So no matter what anyone says it is not there car or bills ,so again go with what is needed.If u r having trouble with fuel cost it maybe worth changing cars,its killing us atm with the fuel cost.

No, she can not.

No.
Some cars only recommend it.
But the G35 Coupe has a powerful engine with 290HP.

An engine that powerful needs premium fuel to work.
Most sportscars and luxury cars with powerful or turbocharged or supercharged engines require premium fuel.

They have a different fuel chamber only made for premium.

You can but only if you are going to keep the car for 3-5 years, it will need injectors. The real fact is that you should not buy a premium car if you do not have the budget for it.