Ok so I noticed a Bolt missing on my engine today, I have been driving at least 60k miles like this. The bolt identified in red on the right is in a similar location to the one that is missing on my engine, the area to the left identified in red, is sort of what it looks like on my engine, like a little hole, but that hole does have threads on the inside of it. What is the deal, what are these bolts, on my engine there is a bolt like directly next to it. Basically I am asking what are these bolts, and why is one missing, I bought the car like this because I have never had any engine work done.