spec v oil change( Long)

[Fletcher Moon]

For fear of starting a dreaded oil thread I do have a question. My 02
Spec V has 49000 miles on it and up untill now I've changed the oil at
the dealer every 3000 to 4000 miles using Castrol 10W40 with Nissan oil
filters. I mentioned to the sevice guy at the dealer I was thinking
about switching to Mobil 1 and extending my oil change intervals to
about 5 to 6 thousand miles since I put a lot of miles on my car.He told
me that they got a service bulletin from Nissan advicing against useing
synthetic oils.Are any other listers aware of this or is he just feeding
me me a bunch of BS.
TIA
Fletch
02 SPEC V