[Robert1101]

Could it be trans Fluid? Possibly a leaking cooler line or cooler at the radiator causing fan to pull the fluid from the leak and blow it onto the engine?

If it was tranny fluid the engine would not be down 2 quarts of oil. (assuming that he checks it regularly)

 

[Robert1101]

Just a follow up and what I now think.

It took quite a bit of effort (and cursing of the installer ) to get the filter off last night. I was really hoping to find some evidence of the cause of the leak but it all looked OK. The gasket was in place clean smooth and no wrinkles. I decided to replace the filter anyway just because.

In comparing the old one with the AC Delco replacement the filters appeared to be identical. Perhaps the diameters were a fraction of a mm different, perhaps. Close enough.

I then checked the Mating Surface(MS)(not sure what to call it) on the block that the gasket mates up with when you screw the filter back on. It was free of knicks, scratches etc... then it hit me.

$set wild_speculation = Back_On

The MS surface is a bit wider( a couple mm ) than that of the gasket. Once the filter is in place the outer portion of this surface is exposed to the elements. No problem but over time this shoulder area will build up with oil soaked dirt baked hard by the engine temps.

Again no problem come next oil change if this shoulder of crud is cleaned off or the new oil filter precisely matches the diameter of the old one. My assumption is that this shoulder of crud is rarely ever cleaned off.

Lets say a filter with a slightly smaller diameter is installed at some point. This would allow some crud to build up on the newly exposed shoulder area of the MS. Then lets say next filter change a "normal" diameter one is installed. At this point the gasket of the new filter is going to be installed partially on top of the newly formed crud. If the crud is smooth stable and not overly thick the gasket will likely seal with enough torque. Repeat bigger-smaller gasket size process enough over 169,000 miles of oil changes without ever completely cleaning the MS you will have a pretty good crud layer and possible failure point.

I'll admit that I have never cleaned the oil filter MS. Mine had a pretty good layer of baked on crud all the way around. I'm bet the folks at the quickie joint never clean it either. Doing so last night took quite a bit of scraping and rubbing on my part.

Therefore: My story line (as of this morning) for the failure mode is now as follows. The last oil change installed a filter whose gasket overlapped the built-up shoulder crud on the MS. They torqued it done to get it to seal and sent me on my way. On the way to the movies a portion of that shoulder crud underneath the gasket decided it was time and let go. The pressurized oil now had a pathway to freedom. Once pressure was stopped by turning the engine off when I popped the hood the gasket was able to expand enough to fill the void and able to hold back the pressurized oil when the engine was restarted.

$set Wild_Speculation = off

My New Years resolution: I resolve to fully clean the oil filter MS each and every time.

In all honesty I believe, in time, you will find another cause.