Oil leak on start up

[blown motor]

Let me give you the back story on the pictures. Last year, this started happening in August I think, I would start the Challenger (340), drive it out of the shop and go for a run. When I got home and backed it in the shop I had oil drips across the floor in the pattern seen in the second picture. This morning I fired it up for the first time and let it sit two or three minutes on high idle before moving it. Drive about 6 miles, engine was up to temperature. The first picture is oil on the cardboard under the car. That happened in that first two to three minutes. I did not park over the cardboard when I returned.
I now believe that my oil leak is happening on start up and quits when the engine warms up. I couldn't find any drips in the yard and there were no drips from pulling into the shop. Just one drip on a piece of cardboard that I shoved under the car when I got back and shut it off. It had sat about 5 minutes.
Any thoughts?

[blown motor]

I pulled the car into the shop after the first run and let it sit about an hour and a half to cool down. Started it, backed it out, did a few miles to warm it up again and backed it in again. No dripping. So this is clearly a cold start up issue.

[jimynick]

Murray, could it be an oil pressure spike, at cold start-up? Could the filter be leaking? What side of the engine does it leak at?

[Jay Bee]

Yeah, what Ian said. What oil grade are you using?

[blown motor]

Using 10W30 with STP oil treatment. Same as I've done for 10 years. I'll watch oil pressure gauge closer on next startup but I haven't noticed it being any different than normal.

[Bullitt-]

  A quick search turned up this Ford with the same symptom
https://www.ford-trucks.com/forums/1770244-oil-leak-only-on-cold-start-up.html

   Problems was with the oil filter.   

[blown motor]

Thanks @Bullitt- I think I'll put the car on stands, start it and get a good look underneath. I hope it is the filter, that would be an easy fix.

[blown motor]

You called it @Bullitt- I got back at the car today and oil was flowing down off the filter when I started it. I changed the filter and it seems to be good. It was a NAPA Gold filter which I think is made by WIX, but I could be wrong about that.

Do filters have a bypass valve or pressure relief valve? Cold it have stuck?

[Bullitt-]

        Glad you found the issue   

 There is a bypass mechanism but I don't think that would cause a leak.

More likely a seal issue, I read about the old seal sticking to the block causing leaks.
  I've caught this at least a couple of times.

   Also the Napa Gold may or may not be made by WIX, but none should leak.



https://www.familyhandyman.com/article/why-is-my-oil-filter-leaking/

[BIGSHCLUNK]

Ya, NAPA Gold used to be WIX. I hear it's hit or miss now

[cuda hunter]

It sounds like it is a deteriorating rubber seal then?

With tires being made with less oil and cheaper products I would assume all rubber parts are being made cheaper.  Hence the deterioration.

  When it heats up, it then expands the rubber and seal the leak ??