This was an exceptionally bad move.I had put some Sea Foam in fuel when I thought it was bad fuel. Would this have caused some additional problems? The black smoke coming out exhaust is new concern, may be coincidental.
Who ever told you to do this should never be trusted with your car again. Ever.
In a word: yes. You must only use a dexos2 oil. Ever.gregbonat said:At 158000 miles is it still necessary to only use dexos 5w-30 oil?
Using a dexos1 or some other kind of oil will lead to multiple system failures such as you've described.