as i understand it, the synthetic oil itself does not break down. so, technically the oil is fine. however, contaniments can be introduced. my oil turns very dark or even greyish black after > 3-4k mi. yeah, i realize oil can change color and be fine. but personally i'd rather be safe than sorry.

 

Using Mobil-1 now and will be staying with it for the life of the car. Changes between 5-6k are very reasonable with any synthetc and to do a change more often is really not cost effective IMO.

 

royal purple

 

I was/am using Mobil1 synthetic, but will be switching to redline on my next change.

 

sperm whale oil.. top that for rare oil..

but I use Mobil1 in all my cars and do a 10K oil change interval in all them..

 

Castrol Syntec 10W-30 changed every 3000 miles.
K&N Oil Filter.
121000 miles. Unfiltered ITBs.
Consumed 1.75 quarts between 118000 and 121000.