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Discussion Starter #1 (Edited)
I took off the engine cover this evening to dust off the engine surfaces and keep everything nice and clean. I noticed shiny black spots concentrated in one corner area of the engine, and then I touched it. I believe the greasy residue is oil (I didn't smell gas). The shiny specs seem like the engine sprayed mist of oil around that valve (I believe that's a valve, I'm not sure).

Am I leaking oil and should I be concerned? Could this mean that there is or could lead to damage to the Turbo?

I drive my car (I bought it brand new) like an old lady, but I do live in Los Angeles with stop & go traffic every day.

2018 Mazda6 Grand Touring Turbo (21K miles)

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Oil control valve, it appears to be a common thing to leak. Whether it's a real problem or one you can just wipe off every now and then depends on the volume.

20,000 miles? I'd be a bit unhappy but maybe not enough to rip it apart and fix it. The reason is that you may actually wind up with more of a seep by screwing with it than leaving it alone. Since you're under warranty I'd make a bit of a stink with the dealer, but again, the caution is that it's not hard to wind up with more leak rather than less when you remove valve covers and such.
 

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I discovered the same thing on my 2018 Signature.

The part the dealer said they needed to replace was actually part of the entire valve cover, so the whole thing needed to be ordered. The odds that the new one will leak too are high as @tickerguy mentioned, it's a common issue on the 2.5, both turbo and non. It's a gamble for sure whether it would be worth the effort tearing it apart to replace. Probably be good to make the dealer aware of what you've found so it's in their system.
 
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Discussion Starter #4
How did it start to leak? I don't drive the car hard - to be honest, I can't. I live in Los Angeles with stop & go traffic.
 

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How did it start to leak? I don't drive the car hard - to be honest, I can't. I live in Los Angeles with stop & go traffic.
That's a good question. I suspect if it was an easy answer/solution it would have been rectified by Mazda years ago, I think it has to do with the design and where the decided to put the OCV. I assume vapour is leaking out around the rubber seal and the vapour has oil droplets in it and they are being deposited around the seal on the valve cover.

Different manufacturers put these oil control valves in different spots. The Honda design approach (like in my S2000) uses bolts to hold it on the side of the engine block, but it looks like the Mazda approach doesn't actually use any fasteners to secure the seal between the valve cover and the OCV, so by nature it doesn't seal as tightly. Mazda just relies on the pressure of the gasket against the oil control valve body to seal which wouldn't be 100% tight.
I am doing some heavy MANsplaning here. I really have no idea.

Here are the S2000 ones...there are 3 bolts holding it on, and they still leak after awhile. It's actually 2 separate pieces (the triangle-shaped one attaches to the more square one and then the square one attaches to the engine block), so there are 2 gaskets that can eventually fail. My S2000 has a slight leak on this part so I've got a new gasket that needs to go on this winter.
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