infiniti service recommeds castrol highest quality NON synthetic for G35 coupe's...why is that? is this because the car did not come with synthetic so dont use synthetic?
i also asked about oil filters and which one to use....they said to use the oil filter infiniti puts in the g35coupe stock...they tell me it does the best job...

so for my oil change coming up i should not use sythetic oil?

 

could this have something to do with the seals not being used to synthetic oils?

 

When I bought my 2000 Maxima new, the dealership
recommended that we not use synthetic oil....because
they considered it a waste of money since we still needed
to change it at 3750 mile intervals. There is nothing wrong
with using synthetic oil. I suspect this is the reason Infiniti
says the same thing. I changed to synthetic in my G35 Sedan
after I bought it used. No regrets.

2003 Twilight Blue Sedan 5AT, sunroof, leather,
splashguards, GG red 7 wire Hypergrounding kit, 350Z intake duct(soon), K&N filter.