I was shopping Michelins and TireRack and Discount Tire both have the standard 225/40/R18 Pilot Sport 2, but at TireRack they give 88Y and at Discount Tire they have 92Y. I figured I'd hit up the brain trust here to clarify this.

 

Load rating of 88 equals a load capacity of 1235lbs, while a load rating of 92 equals a load capacity of 1389lbs.

What load rating did the car come with originally? What is the recommended load rating on the door jamb tag or in the owners manual?

While you don't want to fit a tire with too low a load rating too high of one can possibly deliver a harsh ride.