I feel this topic is the heart of my concerns and many out there with new vehicles desiring longer OCI from a synthetic.
I've ran GTX 5w30 in my 04 Maxima from 1000 miles with the reccomended OCI of 3750 w/ oem filter. Coming up on my last change before 20k mark when I plan to switch to Syn. I'm currently on the fence about either M1 or Amsoil. (I'll decide that in other threads, but this may help my decision.)
Drove 15k the first year, but plan to cut back those miles by driving my old buick (which I got back recently) during my 5 min. commutes. Since the Max will take on less short trips, I feel just fine extending my OCI to 7500, especially with a SYN.
I know syn will last much longer, but like others I have warranty concerns. I know it's over-cautious since I bought the car hoping to join the high mileage club and Syn can handle it.... but don't want the headache if something arises.
Since I have a stockpile of oem filters, should I just run the 7500 interval for the filters and Syn? (since the manual states 7500 as acceptable, i assume that goes for the filter too?) or go 10-12k/1 year intervals with filter half way and not worry about the warranty?
With warranty in mind, how do I prove I'm doing acceptable intervals anyway? Should I save all my filter boxes and empty oil jugs? I record my changes, but only kept my large filter order receipt.