RECOMMENDED OIL WEIGHT on 1998 Nissan Altima

MY 98 NISSAN ALTIMA IS GETTING A replacement with a 78000 MILE ENGINE. MECHANIC IS PLANNING ON PUTTING IN 20/50 OIL VERSUS 30? my bad engine had that heavy weight because it was worn out. WHY would he make choice for such heavy weight? I LIVE IN FLORIDA AND HE CLAIMS ITS BETTER BUT?????

Asked by for the 1998 Nissan Altima
go with the recommened oil weight from nissan - should be 5-30 or 10-30.i would also use castrol gtx or castrol high mile oil.
1 more answer , 2 more comments
20W50 is too much for that engine. Even in FL 10W40 is enough for your Nissan.
Use a good quality oil, like Pennzoil and replace it every 3K miles.

what about straight 30 or 40 versus 10W?