Originally Posted By: tc1446
Have always used syn 5-30 in the Altima and now the Accord calls for 0-20. Aside from warranty issues with Honda, I'd like to use the same oil in the two cars. Any reason not to go with a good syn 5W-20, particularly in the Altima? In the relatively mild climate here in central N.C. I can't see any reason not to use it in the HOnda.
To answer your question (and assuming that we take warranty concerns completely off the table for a moment)... If your Altima is a 2.5 L 4-cylinder engine, then I wouldn't have too much of an issue using a 20 grade oil in it under the right circumstances. Nissan now specs 20 grade oils in their 2.5 L QR engines and not much has changed over the years. The QR seems to do well on thinner oils, as it does not heat up or shear the oil nearly as much as the Nissan VQ or VK engines do.
That being said, if your Altima is a 3.5 L V6, do NOT use the 20 grade oil.
If you do want to use a 20 grade oil, I'd choose a high quality 0W20 synthetic over a 5W20 unless you are always doing longer highway drives and no short tripping. But again, we're splitting hairs here.
If it were me and those were my cars, I'd be more inclined to choose oils based on all of the different factors involved (type of usage, mfg spec, environment, cold starts, etc, etc), and if I ended up with the same or different oils, so be it.
Cheers...