Hello I got a honda civic with integra gsr motor with around 80000 miles on it i got a bad head gasket so im going to replace it but i was thinking my car since i did the motor swap has had black residue from the muffler on my bumper and after an oil change my oil gets dirty again in like a week i have heard that it could be my piston rings and since im going to take my head off should i replace them i heard all you got to do is take the oil pan off and push the pistons up to the head but i talked to my mechanic and he really doesn't think it could be the rings he said if it was oil it would be blue not black he said that most likely im running rich on gas. what do you guys think any feed back greatly appreciated thank you