bubbles in oil

[matthew]

i saw some folks viewing this forum and hoped someone could answer quickly. i'm in the middle of a project and could use some info right away. i've turned up little to nothing on a search.

quickly...
i rebuilt the top end of my '92 4rnr and this evening completed. went to add the oil back in, realized i overfilled, drained to start over, and discovered bubbles in the oil....plus a slight greenish tint. i noticed when i drained the oil it came out very dark at first, meaning i hadn't drained the oil when i started the rebuild. could have swarn i did. that was over a month ago when i started the project. anyway, the oil i added tonight was synthetic Mobil one. should be compatible with regular dino, right? it is cold, the original oil is dark and aged and has been sitting. could these be the possible causes for the bubbles...the mixing and the age?
and what of the tint? i figure the oil just has to be rather broken down because no headgaskets leaked and no coolant got in the block during the tear down. if any did, it was very, very little...but, i'm pretty certain that couldn't have happened. anyhow, can anyone offer some suggestions on the oil. i just want to use it to crank the motor and test it for success or failure on the rebuild....see if it runs.
hope this isn't a stupid question.

thanks

 

[jorton]

I think the green tint is dye. Regular Mobil oil is that color, too.

And I think bubbles are from draining the fresh OC cold. I never see bubbles in hot used oil.

 

[porcupine73]

What cooler coolant is in there?

 

[porcupine73]

Drats that no edit button. What color coolant is in there?

 

[Trav]

I would drain the oil,leave the oil drain plug out and pressurize the cooling system.Look for pressure drop or anything coming out of the drain plug.I believe you can rent a pressure tester at some chain auto parts stores.If no drop and nothing comes out of the drain hole go ahead and fire it.A pressure tester will tell you if the cooling system isn't holding pressure but you need to know if it does leak down is it going into the engine internals.