What is the plug gap for a 1999 Subaru Outback 2.5?
.030" to .035"
The actual spark plug gap should be listed on the emissions sticker on your hood. You would remove the spark plug, and use a feeler guage, or a spark plug gap tool to the gap specified on your emissions sticker. You would increase, or decrease the gap between the center electrode and the end of the plug. Hope this helps. mudmanben