If the gaskets are leaking, then it could be. If your gaskets are leaking you will see some oil in one, some or all of the spark plug reservoirs. The front is not too hard to replace, while the rear is a little more involved. The gaskets for the front and back only cost about $20 a piece. I got mine from the Ford dealership since there aren't any Mazda dealerships close by. If you need to replace the rear gasket it is also a good time to consider the phenolic spacers since you have to replace that gasket when you take the intake off. I think the phenolic spacer will run you around $60.
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