I Bought my 2007 Mazda 3 I Touring 2.0L in June 2007. Since then I have put 27,000 miles on it and I am very happy with it. The only thing that has bugged me is a clicking noise that developed about 6 months in. The clicking seems to come from under the valve cover and it is there whether the engine is cold or hot. I did some searching on this issue and it seems that it may be a valve in the intake manifold causing the issue.
Now, I guess it wouldn't hurt to bring my car in to have it checked out. In fact, I actually setup an appointment a few months ago with the dealer but the line of questioning done by the person at the service desk freaked me out and I ended up canceling the appointment. What got me worried about my warranty coverage is the fact that I switched to Mobil 1 full synthetic 5W-20 at just over 3,000 miles and have been using that ever since (changing every 7,000). The person at the service desk made it sound like that was a bad thing and that my warranty was in jeopardy for doing that. Maybe I'm just jumpy but do I have anything to worry about?

EDIT: Why does the forum keep adding apostrophes into my posts? I keep deleting the extra ones on "wouldn't" and "I'm" but they keep coming back! Weird!

 

I was reading about this a few weeks ago because my friends m3 (BMW :P) had a similar issue
Its called Valve tick
His mechanic told him to get something called Rislone from autozone (or any place similar, even walmart)
Its a yellow bottle and you put it in with the oil

His engine has pretty much no ticking now

 

Thank you for the reply. I wanted to add something to my original post. The engine idles just a little rough. I remember when I bought it I could barely tell the engine was running but it now has a definite shimmer when idling.

 

I would bring it in to get it looked at, since the synthetic oils meet or excede all of Mazda's specs for oil there is not alot they can say.

 

have you tried the Rislone, please let us know what happens if you do. Thanks.
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I have not tried it yet but I guess I will before taking it in. I just changed the oil yesterday though. It's topped off and I can't add anything to it.