What's the 2008 honda pilot oil drain plug size?

The oil drain plug on Your 2008 Honda Pilot will measure 16mm hex if it comes directly from the manufacturer, though many aftermarket parts will measure 17mm as it is a more common size. You can use a box wrench to attempt to mitigate any rounding, though the drain bolt should not be overtightened; it has a very specific torque spec. Specifically, You'll need to torque to 29 lb-ft, +/- 1 lb-ft. Always remember to replace the crush washer with a new one each time You remove and replace the drain plug. Any under tightening and You run a significant risk of an oil leak; any overtightening and You run a risk of serious damage to the drain plug, or the aluminum oil pan itself.