I'm thinking about adjusting my valves today. Does anyone know the acceptable clearance ranges for the 6th gen I4 and the benefits of adjusting to either end of the acceptable range? tight vs. lose vs. somewhere in the middle?

 

The clearences are located underneath the hood on an engine emmisions label.

It is always better to have them too loose than too tight because if they are tighter than the clearence specifed, you can burn the valve, and that is not a good thing. I always aim for the middle, between high and low values. I know I've got it when the next thicker feeler guage won't fit.