Been curious about this for a while now. My wife's Toyota Sienna requires 0w-20, but the book says you can use 5w-20 in an emergency, but must change back to 0w-20 next OCI. Other than cold start properties and higher PAO in 0w-20, why would using a 5w-20 vs 0w-20 in California be a problem. For the record, not planning on switching away from 0w-20. What is it with 5w-20 vs 0w-20? Just curious. Thanks.
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