RE: 1999 Civic Si (non Vtec) Is Hi-Octane Really Required?
 

When you go to Canadian Tire, they should have a book in the isle with the sparkplugs, just look it up in there and they will have a listing of all spark plugs that will work with your wengine that they carry, or you can pop the hood and on your timming belt cover it will have a sticker that will say that reccomended spark plug, (NKG is OEM for it)