I got an after market oil pan gasket for my civic only to take it apart and discover the original part is a round gasket (like an o-ring) and the new part is a flat gasket. I tried the install any way and now have a SEVERE oil leak (worse than before). Has anyone has success with flat gaskets? I already have an oem gasket on order to re-attempt the install.

 

I would go OEM on all gaskets, always.

The original gasket is flat. Some would recommend using liquid gasket in addition to the new gasket.

 

The gasket I removed is round. There was a groove cut into the pan where it sits.

 

You must have an aluminum oil pan then. Steel pans use a flat gasket.

I thought the aluminum pans just go on the block metal to metal with sealer, like the case halves of a manual transmission. Never actually did one though.

 

Nope. Actually, I kinda like the design. Just kinda irritated they tried handing me a flat gasket instead. Sitting in the groove of the pan, there's really no way to screw up the positioning.
ANOTHER question: I had a stud break during the install (not where I have the leak now, totally unrelated). A bolt is easier to find than a new stud. Think I could replace the stud/nut with a bolt with no ill effect?