Confused on Bosch Spark Plug Gap


I just bought a set of Bosch Platinum Plus plugs (# 4012 - not +4’s). I have never used these and am confused about checking the gap.

The ground electrode (the tab that curves around over the center electrode) has a V-groove cut into it. The center of the V is directly over the center electrode which is basically about the size of a pin.

The gap for my car is supposed to be .052 - .056. Using a feeler gauge style gapper the gap is .049 - but I’m guessing that the gap at the tip of the V-groove is probably correct. But I don’t know how to verify that.

I have been to the Bosch website and the info they provide does not address this at all (which I find odd). It does say that you DON’T adjust gap on Platinum +4 or 2’s but that on others you might need to - but it doesn’t say a thing about measuring this gap given that groove in the electrode.

It might not matter much - I don’t know how much of a gap difference makes a difference. Shall I just trust that the plugs came properly gapped from the factory?


You don’t gap platinum plugs. Install them with the gap they came with.