Originally Posted by vaultwit
*meant to say 2013 in the title, not 2012... Won't let me change now
I'm having some issues with the service center, and I need to know two things:
1) does 2013 altima REQUIRE synethic engine oil, or is conventional ok?
2) if my car had synthetic before, is it safe to switch to conventional?
First off I'd like to say that most "synthetic" oils in America are actually not true synthetics anyway, but rather group III highly refined Dino/crude oil. So really you're just getting a higher grade oil when you buy "Synthetic", and they are just better blends and additives. In this country "synthetic" just indicates that the oil meets certain standards, not so much how it was made or where it came from.
Now to answer, no you don't need synthetic in your 2013 Altima QR25DE 2.5, but you SHOULD use 0W-20, API Service SN, as stated in the Manual. It also says 5W-30 may be used and will be considered acceptable for warranty pourposes, though it is not the recommended product. I believe 0W-20 grade oil is only available in group III and above blends which have been determined legal to call synthetic here in America.
For your second question, it is ok to switch from synthetic to regular oil or even to mix them, but mixing will negate much of the advantages of the higher end oil. Secondly, most likely the Synthetic you had before was not really synthetic, so you're not really switching types of oil anyway!
A few exceptions to most "synthetic" oils being just Group III Dino Oil include High end synthetic oils from Redline, Royal Purple, AMSOIL, European Castrol Synthetic, Extended Performance Mobil 1 (only the Extended Performance), Ester Oil, most of these are true synthetics. There exceptions with these brands too, such as AMSOIL XL that is 85-90% Group III Dino Oil.
Better oils do offer better protection, but even a quality standard conventional oil, in a well maintained engine, can help that engine last a very long time. My family has had cars go 250,000 + miles on conventional oil, with no engine work done other then maintenance. They were still running strong when sold. I personally prefer to use a true synthetic, but it's not a requirement by any means.
Lastly I'll add that I believe the only reason Nissan recommended the 0W-20 on the 2.5 QR25DE is to help achieve better MPG, a big goal they had in the design and specifications of this car. Running a much thicker oil can damage an engine, but the difference between 0W-20 and 5W-30 is not enough to cause any sort of damage, and this is backed up by Nissan's statement that 5W-30 may be used in this engine and will maintain the warranty. Also note that those of us with the VQ35DE 3.5, 5W-30 is the recommended oil.