I have a 2011 Corolla with 2ZR-FE engine (1.8 L), live in Southern California where normal year-round temperature range is 50-90 F (10-32 C), occasionally 40-100. Most of my driving trips are short-run in the city, but much of the mileage (a little less than half?) is on high-speed freeways. In an oil change last week, it was filled with full synthetic 5W-30.
____For me, engine protection is more important than higher mileage. And cold-weather starting isn't relevant here in SoCal, although cold-engine protection (before it warms to its operating temperature) is relevant in all climates, favoring 0W over 5W. The car hasn't been running hot, so this (favoring 30 in 20-versus-30) isn't a factor. For best protection of the engine, is my current 5W-30 worse than 0W-20 (it's recommended in the owner's manual as “the best choice for good fuel economy and good starting in cold weather”) or is it better, or worse in some ways but better in others? And if 0W-20 is better, by how much? (i.e. should I do a re-change ASAP back to 0W-20?)
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____I've read many posts in several forums, and have seen two theories. One proposes that Toyota recommends 0W-20 mainly to help its fleet do better for CAFE standards in USA. The other explanation is that their newer engines, beginning in 2009 with 2ZR-FE (and 2AZ-FE), are designed -- with closer tolerances, etc -- so that, for best protection, the flowing-SPEED of the oil (0W-20 better) is much more important than its thickness (5W-30 better) because the thinner oil can “get into places” and “cover everything” more quickly and completely. Also, the new thin oils, like synthetic 0W-20, are better than they used to be.
____To support the “CAFE theory” some post-ers have said that manuals in other countries (not USA with its CAFE) recommend thicker oils. Is this true, in Europe, Asia, Australia,...? One example is a manual from Australia recommending any of several heavier-weight options, but when two people asked “is this manual for 2ZR-FE or an older engine” there was no response. And a thread with topic “2ZR-FE oil” in 2010 in an Australia forum (toyotaownersclub.com) begins by saying “the manual recommends 15w-40.”
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So... which theory (CAFE or flow-speed) better explains why 0W-20 is recommended by Toyota? And which oil, 0W-20 or 5W-30, protects better? and how much better?
____For me, engine protection is more important than higher mileage. And cold-weather starting isn't relevant here in SoCal, although cold-engine protection (before it warms to its operating temperature) is relevant in all climates, favoring 0W over 5W. The car hasn't been running hot, so this (favoring 30 in 20-versus-30) isn't a factor. For best protection of the engine, is my current 5W-30 worse than 0W-20 (it's recommended in the owner's manual as “the best choice for good fuel economy and good starting in cold weather”) or is it better, or worse in some ways but better in others? And if 0W-20 is better, by how much? (i.e. should I do a re-change ASAP back to 0W-20?)
____
____I've read many posts in several forums, and have seen two theories. One proposes that Toyota recommends 0W-20 mainly to help its fleet do better for CAFE standards in USA. The other explanation is that their newer engines, beginning in 2009 with 2ZR-FE (and 2AZ-FE), are designed -- with closer tolerances, etc -- so that, for best protection, the flowing-SPEED of the oil (0W-20 better) is much more important than its thickness (5W-30 better) because the thinner oil can “get into places” and “cover everything” more quickly and completely. Also, the new thin oils, like synthetic 0W-20, are better than they used to be.
____To support the “CAFE theory” some post-ers have said that manuals in other countries (not USA with its CAFE) recommend thicker oils. Is this true, in Europe, Asia, Australia,...? One example is a manual from Australia recommending any of several heavier-weight options, but when two people asked “is this manual for 2ZR-FE or an older engine” there was no response. And a thread with topic “2ZR-FE oil” in 2010 in an Australia forum (toyotaownersclub.com) begins by saying “the manual recommends 15w-40.”
____
So... which theory (CAFE or flow-speed) better explains why 0W-20 is recommended by Toyota? And which oil, 0W-20 or 5W-30, protects better? and how much better?
