service engine light - too lean
 

I have a 05 3.0 with 7500 miles on it. Over the last few months I've had my service engine light go on 3 times.. maybe over 5 -6 mo or 5 K miles. When I scan for the code I get an error indicating that one of the cylinder banks has gone lean. This last time I got an indication that both banks went lean. It happened while driving in traffic at a very constant and slow speed. The other time, it happened shortly after startup. The first time it happened, I was running plus grade. Never heard any ping, but the light convinced me I need a higher octane. Now I only run 93 octane and I've gotten the light again. I've read that a lot of people get the light on, run to the dealer just to have the dealer reset the light. Is this what I'm experiencing or should I go into the dealer?