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You're much more likely to find that oil is leaking onto the lines in the engine bay and following them into the passenger compartment.

 

It's probably refrigerant oil. How's your A/C working?

 

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The oil cooler most likely has an internal leak allowing oil to get into the coolant. If this is the case, I would think that there's coolant in your oil too.

Don't use the filter adapter shown in the link you provided. Use an adapter that has a bypass.

 

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Using an adapter without a bypass will allow full flow of oil through the filter. It might not burst the oil filter can, but I have heard of the filter media getting damaged and sucked into the oil system lunching the engine.

There was a story about this on www.bobistheoilguy.com recently (one or two years ago). I tried searching for the thread, but I couldn't find it.

Of course a lot of factors are at play here; grade of oil, oil temperature, filter and filter media, etc. I would still avoid adapters without a bypass.

 

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