I went to buy some NGK 3330 for my car and the person at O'Reily's was saying they were really cheap plugs....well they were only $1.49 a piece. I was told by my mechanic who I trust - those were the plugs to use....what's the deal? Are they really that cheap or are they giving me the wrong plugs. The person at the desk said these will ruin my car. Can anyone help me? Wish I could search. Thanks.