Nissan Repair: Gas pinging?, octane gas, shape thanks

Question
I have a 2003 Xterra with a V6 (not supercharged).  When I put in 87 Octane I get a slight pinging with the engine.  When I put in 91 it "rough idles" if I'm in Drive.  If I'm in neutral it runs great.  Is it a spark plug issue or do I need to stick with 91 Octane?  The vehicle only has 64000 miles on it and is in great shape.  Thanks!

Answer
Wade,

The timing will adjust to the fuel you use.  The knock sensor will compensate by retarding timing with the lower octane gas.  I would not think the gas would cause the rough idle, in drive, with premium fuel.  I would look at replacement of the plugs and a full tuneup if one has not been performed in the last two years.  I use premium in everything I drive.  But, that is me and I know I am probably a nut for doing so.