Oil leak diagnostic on a local members car.

[Dev]

 A local member texted to me that he discovered an oil leak under his car. The car was sitting for a good four months or so while he was recovering from shoulder surgery.
 
He brought the car over to the house and I looked under the car to find the leak. The owner has one of those aluminum G-pan oil pans and my first suspicion is that its leaking either at the welds or the drain plug. 
 
 This is what I seen.

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 Only the bottom half of the oil pan was wet with oil on both sides. It was odd because if it was the drain plug the pattern would be different. I cleaned up the drain hole and did the wick test, no seepage.
 I then checked the joint between the sealant and the pan, it was dry. As you can see most of the oil leakage is in the area of the flywheel so I concluded that it was the rear main seal. These Toyota vehicles  are not known for rear main seal issues.
  I had a suspicion that who ever serviced the car added too much oil and after checking the dip stick I was right, it was overfilled by a lot.

The owner has a tag in the engine bay that indicates  how much to oil to fill based on the capacity of the oil pan. 
  Lesson to take from this is you never put in the amount of oil specified by a known capacity and you should never trust the aftermarket. You should always check the dipstick during the fill up to make sure you do not over fill the oil otherwise this is what happens. You can damage your engine with too much oil. Any mechanic worth their salt should disregard the customer and do their job the proper way of checking the oil level and then informing the customer that the oil was full. 

 We plan to extract the excess and monitor the main seal. Hopefully it has not been compromised.

 This is why I only trust myself when I change the oil in my cars. I have had a few friends go though these kind of situations with oil leaks of various kinds because of improper filter installation, stripped drain plugs and now this. 

At the very lest you should check the oil level after the work is completed, most never do these days and treat their car like an appliance. Trust but verify.

[Dev]

 A little update.

 The owner brought over the oil extractor so we can take out some oil. It turns out that it was over filled by 3 quarts which is 2.8 liters of oil?

This is troubling. I would understand if it was 1.5 quarts overfilled but not 3. I am worried that there is something about this pan that might be  throwing off the reading or the relationship of the oil level to the crank. 
  I do not want the owner to be under when the capacity of the oil pan is 6.2 liters. 
 
 The only way to know is to drain all of the oil and fill it up and take note. The oil level is determined by its relation to the crank however if there is something in the design of the oil pan that hitting the dipstick slightly it could skew the reading as I read this was a problem for the Elise for the one of the aftermarket pans.

The pan is also design for the 2ZZ not the 1ZZ and therefore the baffles and sump (including pick up tube) was design around that. For this particular pan the flat baffle sits lower which is not the same thing as the 1ZZ pan that has a windage tray at a certain hight incorporated in the pan. This can have negative effects. 

  The 2ZZ and 1ZZ sumps are different even though the oil pans fit. This is what gets people into trouble particularly those that try to adapt the 1ZZ pan to the 2ZZ.