alright so my d15b7 as about 110000 miles on it and knocks a little the only thing iv'e done is stright back exhuast with no cat, ngk plug wires and a cold air intake.... The problem is that when i get on it i can smell either gas or oil, and i sont know if the oil is low cause the sip stick is worn to much> IF ANYONE knows whats wrong or if this is normal let me know also can someone tell me what kind of oil i can use and what the dip stick is supposed to look like